⚛️┃physics

[potent nova]

ohhhh

i see what your saying now

its one sprite that represents both bands

would it just be easier to have two though?

[woeful pulsar]

Easier than?

[potent nova]

animating the one sprite

or is it easy once I learn the method

[woeful pulsar]

It is the exact same operation, repeated twice for the scenario where you use 2 sprites instead of 1

so not easier nor harder. The same, really.

[potent nova]

i just want the result so ill do any way

thanks ill try implementing it and let you know

[potent nova]

whats the best way to calculate force on a 2d projectile

i want it to change with the velocity of the projectile and it's mass

i know force = mass* acceleration from mechanics but how would i translate that when using velocity that works under gravity

[silver moss]

Like calculate the correct force to hit a target?

While taking gravity, mass, drag etc. into account?

[potent nova]

The force needed to break an object will have its value set, and then the projectile hitting it would have a variable force taking into account mass and velocity

Idk about drag since I don’t think that’s in my game

[silver moss]

Sorry but it's still really vague to me. Break an object?

force taking into account mass and velocity
In what way?

[potent nova]

A projectile from a slingshot will be fired

The velocity will change over time due to gravity

If it has enough force, it will break a wall

[gleaming glacier]

I'm a Unity3D person but i think you would just do the position subtract the last position and then get its magnitude.

[potent nova]

That’s what I did when firing it to get the starting velocity

And direction

But how would that work for force

If you could break it down since I’m a newbie

[gleaming glacier]

Because getting the magnitude is basically getting the Vector2 or Vector3 in float form

So basically its speed

[potent nova]

The speed when it touches the object I want to break?

[gleaming glacier]

Yes

[potent nova]

I will try that thanks

[gleaming glacier]

After that you can do if its greater than a certain amount

get the velocity magnitude

then compare it to a value

[silver moss]

Or just rigidbody.velocity.magnitude

Ah but it's a collision? In that case yes you need to store the last position in a variable and calculate the velocity from that

Or use collision.relativeVelocity

[gleaming glacier]

That would work as well

[potent nova]

thanks didn't know that was a feature

[potent nova]

is that the velocity just when it collides?

[silver moss]

Yes

Well, the relative velocity. So if the other object is moving away at the same time, the relative velocity will be smaller

That's how I understand it anyway

But yeah it's what you probably want here

[scarlet egret]

Hi, I'm creating a motorcycle racing game but I'm having a lot of problems making the motorcycle steer in a realistic way. I'm actually applying a force directed to the direction of the motorcycle to make it move but it's actually like sliding on ice. Any ideas on how to make the steering better? I would like to use physics to make the bike move and steer

[proper sluice]

i have a polygon collider 2d on my stairs with a 45 degree slope so the player can go up and down them, but the character slides down when there's no player input. what should i be doing here to get a good feel/functionality? i didnt really like the bumpiness of having the collider match the block shape of the steps

[timid dove]

A couple options:

• increase friction on the stairs
• have you player controller detect slopes and apply a force in FixedUpdate to counteract the sideways force from the slope (pretty easy to do - you just project the gravity vector on the slope normal, and apply that force in the opposite x direction.

[tender crow]

I'm trying to convert this to the unity.physics equivalent: Camera.main.ScreenPointToRay(Input.mousePosition)
any pointers?

Is this correct:
RaycastInput input = new RaycastInput()
{
Start = Camera.main.transform.position,
End = Input.mousePosition,
Filter = new CollisionFilter()
{
BelongsTo = ~0u,
CollidesWith = ~0u, // all 1s, so all layers, collide with everything
GroupIndex = 0
}
};

[simple cloud]

Why is the object not being pushed when i walk against it?

[dapper lichen]

I see "isKinematic" checked off on that rigidbody- that would do it.

[simple cloud]

You mean on the object?

if i activate that gravity isnt working

[bitter spindle]

Guys, I have a player with a RigidBody moved via physics; and I have enemies that have also a RigidBody (cause I need them to detect collison with proyectiles and to be pushed back by them) and move via a NavMeshAgent. Both the player and the enemies have non-tigger colliders. But I just noticed that they just get to collide with player if the enemies' RigidBody is set to Kinematic, otherwise they just kinda clip through; shouldn't they just collide if both are RigidBodies with Colliders?

[low edge]

Hello all, what is the assumed units for AddForce? Newtons?

[timid dove]

Depends on the ForceMode you use.

by default it's newtons (ForceMode.Force)

if you use ForceMode.Acceleration the units are just m/s^2
if you use ForceMode.VelocityChange the units are just m/s
and for ForceMode.Impulse, it's kg*m/s

[low edge]

so if I have addforce and I want to mimic the F35A at 43000 lbs of thrust disclosed, I would convert to newtons and just use that number? gotcha

[timid dove]

yes assuming you do so in FixedUpdate with the default force mode.

that being said accurately modeling an aircraft in flight will require applying lot of different forces.

In addition to the thrust of the engine there are lift forces, drag forces, AoA forces and the various pitch/yaw/roll forces of various control surfaces etc

[tired panther]

I am trying to make Magna Tiles in Unity, but (without the magnets doing anything) it just kinda turns into a particle accelerator, here is the GitHub Repo if anyone is willing to look into it!
https://github.com/ICOnce/MagnetGame

[low edge]

I have a nice flight model built out already. I jsut needed to know the units thing

[fossil tangle]

Sticky situation ... is there any way to directly teleport a tree of RigidBodies?

All I can find is RigidBody.position --- which doesn't teleport it, instead it queues up possible values, waits a frame, then uses the last one that was set on ANYTHNIG in the Transform hierarchy.

So ... if "child-RB" moves right, but "parent-RB" moves left ... Unity deletes one of those commands (unsurprisingly: it seems to delete all except the last-to-be-submitted), and both the parent AND the child move right.

[tired panther]

Do you want to move them all the same direction?

[timid dove]

Are these Rigidbodies dynamic? kinematic?

[timid dove]

Also are you sure you mean RigidBody.position and not RigidBody.MovePosition

afaik the former is immediate, and the latter waits to apply it during the next physics simulation step

[light cradle]

why is my gravity so.. floaty, i fall so slow? yes it's the default physic settings, and the rigidbody mass is default... idk what i did but in my other project with the same player prefab it's normal? just another render pipeline but that doesn't make sense...

[blazing acorn]

this model has a box collider and a rigidbody but is falling through the floor?

[timid dove]

It's most likely your code

Mass doesn't affect gravity fall speed BTW

If it's not your code it could just be that your objects are very large and you're experiencing the Godzilla Effect

[light cradle]

hmmm. i used the code from another projects where it worked fine, because i thought the same. but still the same

[light cradle]

everything is on scale 1.1.1 (default capsule for player)

[timid dove]

Without showing us details from your project we can only make wild guesses

[tired panther]

If it's a plane, it might just be clipping through it

I've experienced that sometimes

[blazing acorn]

yeah it is ill try and see if thats the issue

[blazing acorn]

nope

[light cradle]

Idk which details i could show

[timid dove]

Literally anything and everything?
Your code.
The hierarchy of objects and the inspector of the object

[light cradle]

Nah doesn't matter
Just thought there was a setting on or something

[timid dove]

Well there's a gravity setting and a time scale setting. Maybe you changed one of those

[tired panther]

Is one of them aa trigger?

[blazing acorn]

nope its fine i gave up on it lol

[light cradle]

I already said i didn't

[tired panther]

Is anyone up for looking into some weird physics shenanigans that is going on in my project?
https://github.com/ICOnce/MagnetGame
The problem is when you spawn a tile it goes bananas

Short video of the Issue

[timid dove]

What are you expecting it to do?

A short review of your code shows several issues:

• Use of AddForce in Update. It should only go in FixedUpdate
• Use of DeltaTime in a force calculation for AddForce, which is never needed
• transform.Rotate WITHOUT deltaTime where it should actually be used
• Mixing Rigidbody and Transform movement and rotation. You should only pick one

[tired panther]

I will take those into consideration, but also it is doing that (the thing in the video, even if I disable all the scripts, except for the script to spawn it)

So for that video, ideally it should just be still

[blazing acorn]

using System.Collections.Generic;
using UnityEngine;

public class DoorSound : MonoBehaviour
{
    AudioSource audioSource;
    public AudioClip creak;
    bool isPlaying = false;

    Rigidbody2D rb;

    void Start()
    {
        rb = GetComponent<Rigidbody2D>();
    }

    void OnCollisionEnter2D(Collider2D collider)
    {
        if (collider.CompareTag("Player") && rb.velocity >= 0f)
        {
            audioSource.Play();
            isPlaying = true;

            if (rb.velocity <= 0f)
            {
                isPlaying = false;
                audioSource.Pause();
            }
        }
    }
} ```

I am trying to get a sound to play when this door is moved by the player and stop when it stands still however the console says i cant use >= or <= with a Vector3 and a float, i have no clue what to do.

[timid dove]

You want to check the magnitude of the vector

Not the vector itself

Think about it

[blazing acorn]

i only started this stuff a week ago lol i dont know these things

how would i check the magnitude

[timid dove]

By getting the magnitude

And using it in the comparison

[tired panther]

Vector3(number, number, number).magnitude

[timid dove]

https://docs.unity3d.com/ScriptReference/Vector3-magnitude.html

There's no need to construct a new vector

rb.velocity.magnitude is fine

[tired panther]

Riiight

Yea

I didn't think about him already having a Vector

[blazing acorn]

this block of code specifically where it says audioSource.Play();

is generating a nullreferenceerror and idk what that is

[dim fulcrum]

Playing with some destructible props. I spawn premade fragments inplace of props when they're hit. This works great, I like how they bump around, but then my character controller get's stuck on them, especially box fragments with flat surfaces take a lot of walking into them before they slide away. (Using a charactercontroller with a custom push script modeled after starter assets)
I tried lowerinf the mass of my fragments but then they're sent flying when walked into.
(I now had an idea that the custom push script could detect if the collided item is a prop fragment and if yes, push it randomly left or right instead of towards the movement direction?)

[fossil tangle]

My goal is to keep all of them in the same place in world space (unmoved) but for one of their ancestors to change its center. With non-RBs thats easy: move the ancetor's center by DELTA, and move the direct children by -1 * DELTA. Happens instantly, all is good. RBs - with position or anything - goes BOOM

[fossil tangle]

Everything dynamic. Yes, I mean RB.position - it doesn't teleport, and if I understand correctly it is not immediate (it instead queues it internally within physics, along with other things, that gets processed towards the end of the frame)

[timid dove]

MovePosition queues it up

setting the position directly is immediate

Anyway dynamic Rigidbodies don't respect the transform hierarchy

They won't follow their parent objects

[fossil tangle]

OK, well, position doesn't teleport - it introduces force.

What I'm looking for is: true teleport (i.e. no forces applied, nothing changes), which would allow me to keep the RBs at same point in space, but move their parent/ancestor's position.

At the moment I have everything working fine if you don't care about the transform offset - but I do care :(.

And Rigidbodies do 'respect the transform hierarchy' - sure at runtime they (re-)position themselves independent of it, but if you move their ancestor transform e.g. in Editor, they move too.

(which is part of the problem - if I didn't care about the UnityEditor things would be a bit simpler)

[timid dove]

Definitely not.

[timid dove]

To leave it in the same world space position you'd simply do nothing.

[timid dove]

In the editor is different from at runtime. And Transform position is different from Rigidbody position.

If you want to just move things as if in the editor, move the Transform then call Physics.SyncTransforms()

[fossil tangle]

I tried SyncTransforms - it didn't make a noticeable difference. Is there something additional necessary?

NB: calling everything from inside FixedUpdate (maybe that's a mistake when trying to do this particular change?)

[fossil tangle]

If I update transform.position of an ancestor object, which can happen in editor, in editor-playtime, and in player ... if it has descendent RigidBodies that are non-kinematic, dynamic ... then things go badly. The specific 'badly' varies based on context.

If I don't also move the child objects, then everything jumps in space.

If I also move the child objects by "-1f * [amount parent moved]" then things explode.

The best I've managed so far iss:

1. set everything to kinematic
2. update all positions
3. wait until at least one more FixedUpdate frame completes (seems like at least 'current fixedupdate + one more fixedupdate' have to complete, but I haven't tried narrowing it down, I eventyally just gave up and started waiting for 200ms, plenty of time for multiple to run )
4. set everything back to non-kinematic

If I omit step 3, even if I run SyncTransforms - things still explode.
If I omit step 3, whether I update RB.position, transform.position, or anything else I could finde - things explode.

[tired panther]

Interesting thing I just figured out, the bigger the mass of the big main square, the more it flips out

[quaint birch]

What are you trying to achive with the nested Rigidbodies? They usually prefer not being nested (unless they're kinematic, in which case you move them as you see fit)

And that's in 3D, right? Because 2D and 3D tend to behave differently.

[timid dove]

The only typical use case I know of for nested rigidbodies is a ragdoll

[fossil tangle]

Yeah, the underlying problem is that Unity-the-platform (UnityEditor, core APIs, etc) hates non-nested objects - try managing a project with 10,000s of objects without nesting anything (been there, done that, don't want to do it ever again :)).

So I have 10,000+ lines of code that are all 'pure' unity (no physics) that work perfectly - but rely upon nesting in many places. Some of that could be refactored to work without nesting - but some of it would be impossible or very difficult (e.g. all the places that use GetComponentsInChildren<> - some of those would be very difficult to replace - I'd have to re-implement big chunks of Unity itself, write a custom Transform hierarchy system (that doesn't depend on Transform.parent), and I'd have to write all the UI for it - all the EditorWindows, a custom Hierarchy window, etc etc etc).

What I'm doing right now is extending/updating that so that it ALSO plays nicely with physics.

Additionally: my end users 99% of the time want their object-trees to be deformable "out of the box" -- which means one big object, but all the sub-parts have RBs on them.

If I were doing this from scratch, I would have all the sub-parts sit as siblings at the top of the hierarchy (avoiding RBs various allergies to nested transforms) - although then I'd be tearing my hair out trying to figure out how to have a Project that wasn't 10,000 objets in the root.

BUT ... experimentally ... Unity seems fine - 98% of the time - with nested RBs. There's just a few places it goes wrong (this being one of them)

TL;DR: because 98% of this works fine with nested RB's, I'm currently taking the approach "let's see if I can make the final 2% work too - what do I need to change? what APIs do I need to use" ... but if that proves impossible / the hacks become too problematic, I'll consider other approaches. But all the 'other approaches' I've seen so far start with "x months of work to re-design and rewrite everything in ways that breaks all the non-physics use-cases, so requires huge amount of time/design/testing"

[quaint birch]

End users of what, if you don't mind me asking? 🙂 Am curious about the context

Also, can you show current code and example of how broken is it with it?

I can try to setup something quick, but setting rb.position should generally be fine, I think... though, perhaps everything should be done through RBs (or everything through transform, I don't remember how that worked), not a mixture of those 🤔

[fossil tangle]

e.g. without physics, building stuff in-game https://www.youtube.com/watch?v=qfak_-UjIAA
e.g. with Mecanim rigs https://www.youtube.com/watch?v=Rd2M4vPy29U
... then with physics/rigidbodies: https://www.youtube.com/watch?v=TL4gJzNIBJM

It's all the same asset, just different games built on-top.

[quaint birch]

Looks very cool! 👍

[fossil tangle]

Where I am right now:

• RB.position exerting forces <-- I now think: this was probably because I had some interpenetration I hadn't noticed? So although I wasn't moving anything, by the time I executed RB.position changes, an interpenetration was already present, and it wasn't RB.position that added the forces, it was the actual world locatins of everything.
• to assemble things:
• 1 . implemented a replacement for Unity's crappy OnCollisionStay so that I know what colliders are touching each other even when they're sleeping
• 2 . nested RigidBodies, to remain compatible with core Unity -- and so that things like the 'mass' of each individual part are remembered/maintained
• 3 . set everything kinematic
• 4 . use Physics.ComputePenetration to avoid all penetrations
• 5 . use RB.position to move everything to safe places
• 6 . wait a few frames for physics to settle
• 7 . de-kinematic everything
• breaking forces are a pain in my butt - looks like I need to have another "wait a few frames" that waits a lot longer, and converts all joint-break-forces to infinity, then restores them after 'enough time for the physics to settle'

[quaint birch]

Oof... well, good luck with it! It's a little bit too complex for me to try and help, sorry 😅

[fossil tangle]

Same trick is working fine for Breaking-forces, so ... yeah, I think this is the solution to all my 'get unity physics playing nicely with rest of unity': 1. go kinematic, 2. fix positions/suspend break forces/etc, 3. coroutine wait for a few physics frames, 4. restore everything

... although point 3 I'd like to try replacing with a manual call to simulatephysics, maybe I can get away with a fixedDeltaTime of 0.0001f or something, just enough for it to notice that 'oh, you've gone kinematic - let me cancel all forces'.

[rare nebula]

is setting transform.position instantaneous??

Because I have this code

Vector3 TestingVector3 = transform.position;
Ray TestingRay = new Ray(TestingVector3, transform.forward);

transform.position = new Vector3(0, -100000, 0); // This transform should be moved super far out so that the spherecast should never hit it

RaycastHit[] TestingHits = new RaycastHit[5];

int TestingNumHits = Physics.SphereCastNonAlloc(TestingRay, 10, TestingHits, 1, PlayerLayer);

for (int i = 0; i < TestingNumHits; i++)
{
    TestingHits[i].transform.position = new Vector3(0, 100, 0); // However, the final position of the transform is always 0, 100, 0, not 0, -1000000, 0, implying that the spherecast somehow hit the transform despite being teleported wayyyyy out?????
}

and ?? the spherecast always hits the transform object despite it being teleported far enough so that the spherecast should nenver hit it?

[rare nebula]

NVM I fixed it

I just had to call Physics.SyncTransforms() after setting the transform position

[timid dove]

Yes it is but the physics engine update is not part of that, and happens later as you found out

[fossil tangle]

Did the definition of compound Colliders change at some point?

Docs describe (and I am sure this was true for most versions of Unity historically)

• Colliders must be on the same object as the Rigid Body
• Compound colliders must be on children of the Rigid Body

Experimentally in Unity 2022:

• Unity does an equivalent of "getcomponentsinchildren<Collider>" on the Rigid Body - any and all children are counted

...
e.g. (tested just now in 2022-LTS):

1. RB with no other components
2. Child with no components
3. Grandchild with a Collider

<-- is treated as if the grand-child-collider were on the grandparent-RB

but I can move that Collider around, add others anywhere in the Transform tree beneath the RB - even multiple levels deep - and Unity physics still treats it as one big Collider-set

...
And source code I had that originally was written for Unity 5, worked for 2017, 2018, 2019 - is now crashing in Unity 2022, apparently because of this.

(the crashing is fine - I can update it with this definition of "any colliders anywhere in the tree are considered part of a compound collider" - but first I want to check it's actually correct, especially since the docs say different)

"A compound collider is made up of a parent GameObject which has a Rigidbody component, and child GameObjects that have colliders." <-- https://docs.unity3d.com/Manual/create-compound-collider.html

[timid dove]

I'm not sure I understand what you're asking. What is the behavior you believe has changed?

Afaik it has always been that all colliders on the Rigidbody object itself as well as any children grandchildren etc are all part of that Rigidbody

[fossil tangle]

I believe it used to be: as the docs describe today

Two types: colliders (directly attached) and compound colliders (directly attached to children)

I have ... lots ... of legacy code that goes out of its way to support this, because its what Unity defined. From memory - this is a long time ago! - there were many complaints against Unity because of it, especially because it made it difficult for developers to drag/drop complex meshes into a scene and have them work together - only the "topmost" would get detected and used as compound colliders

IMHO the 'all descendents' is easier to understand and work with, so ... this is better if it's the correct current definition

[timid dove]

I don't think there has ever really been a distinction between colliders on the same object and colliders on descendent objects

If that changed it was probably back around Unity 5 (around 2015)

[fossil tangle]

Yep, I remember that coming in, (and I do have some code that predates Unity 5), but I was sure the compound colliders had originally been implemented as children-not-descendents.

I guess I could install some old Unity versions and verify :).

But also: why are the docs wrong, why do they say children not descendents, if it was never the way I thought? Hmm.

[timid dove]

I don't think the docs say children and not descendents

I think when they say "child GameObjects that have colliders" they are including descendents in that

they don't say anthing like "only direct children"

[twilit geode]

Hey guys, i am using physics to detects when to display some interactable UI
But sometimes that doesn't work, its buggy.
I use two Physics.OverlapBox
One is for close range, the other is medium range.

I need some advices with physics and if OverlapBox is a good choice
I am very bad to explain my issues if you need more informations, tell me 🙂

First of all i didn't call the physics in FixedUpdate, that maybe the cause

[twilit geode]

okay thats worse haha

its the 2 OverlapBoxes

[timid dove]

Simpler just to use trigger colliders / OnTriggerEnter/Exit

[twilit geode]

@timid dove So just have to add 2 colliders to my player ?

[dim fulcrum]

omg unity physics is killing me. I have an items layer set to NO collisions with the player, and a targets layer colliding with the player. When I parent an item's transform to a target it's colliders somehow "inherit" the target layer and the item starts colliding with the player. (also I "stick" the item to the target setting it's rigidbody to kinematic, after some time I set the parent to null and set kinematic back to false, so the item falls out of the target and lands on the ground. But if I stand on it before that happens, the player ends up standing on some invisible ghost collider which they were never supposed to be able to stand on (cause its on the items layer). I take it it's just not advisable to change physics objects parents?

[timid dove]

Colliders don't inherit their parents' layers

Show screenshots of your setup, something else is going on

[dim fulcrum]

I know, but when I set my "target" to the items layer, everything "works" (except the target not colliding with the player) so the target layer definitely affects the object being parented to it physics..

Anyway I just wen down the path of replacing the questionable parenting of objects and instead adding a fixedjoint component. And.. I'm getting the same issue. The item, that is normally not colliding with my player suddenly becomes an obstacle when I connected with a fixed joint to an item that is on a colliding layer. (and that "collider" remains there after I Destroy the joint!)

[dim fulcrum]

Well it must be something with my setup, cause I just created an empty project to recreate the issue and it behaves correctly, will try to migrate my actual scripts bit by bit to try to pinpoint what's causing the weird behaviour :/

[dim fulcrum]

@timid dove yes it was something else (of course), thanks for your confidence, which pushed me to try to build a minimal example showing the issue. (it was the simulated "ghost" item, used for a trajectory visualisation)

[timid dove]

Glad you got it working

[scarlet egret]

Hi, I'm actually creating an arcade car game and I'm using physics to make cars steer, so I'm applying friction force to car wheels. Everything works fine when the car is moving and when I stop on a plain surface, but I have some problems when I start the game and when I stop on an inclined surface. Do you know how to fix this?

[dim fulcrum]

I don't but I'd start with the first line, it's grabbing the velocity vector and zeroing the y component. this makes sense on a flat plane, not so much on an incline. I'd start with grabbing the ground normal underneath you and projecting that vector on that plane.

[scarlet egret]

Fixing the first line solved the problem, thank you✌️

[naive orbit]

hey so I have a character rig with hingejoints and when the character flips (inverted localScale.x) the hingejoints get kinda funky, anyone know why this is happening and how i can fix it? (pictured: same character facing right and left)

i've already tried using a Y rotation to flip the character, same issue

ngl not sure if im in the correct channel

[dim fulcrum]

I don't know how 2d physics work (or 3d :), but can you elaborate what "wonky" means, are you sure it's because of the flip? are you flipping / rotaging them individually or some parent object (character)?

[timid dove]

Y rotation is usually better but yeah it's a bit unclear what you mean by funky.

[naive orbit]

im flipping the rig by manipulating a parent object and setting its localScale.x to -1

and by funky i mean the hinge joint is upside down

i imagine i could fix it by adding/subtracting 180 to the upper and lower angle of the joint when i flip but i dont know how to access that in C#

[scarlet egret]

Hi, I'm creating a car racing game and I'm turning using ackermann steering. I'm setting te turn radius from the inspector, but It does not depend on the velocity of the vehicle, so it's not very smooth. How can I calculate the turn radius depending on the vehicle velocity? Is there a formula or what?

I mean, if the vehicle is going faster, the turn radius should be higher

I'm actually calculating the turnRadius like this, but I know this is not a nice way, even if it works hahah

[raven summit]

Hi
How to solve the collision problem between two rigidbodies?
I don't want to use layers because there is a limited number of them and there are many objects that should not collide with each other. I also don't want to use Physics.IgnoreCollision because each object has dozens of colliders and switching them would not be optimal. Is there something like Physics.IgnoreRigidbodyCollision that ignores collisions between two rigidbodies?

[timid dove]

How to solve the collision problem between two rigidbodies?
What problem? You have to explain exactly what you're trying to do before we can suggest a solution. "Many objects" being involved does not preclude the use of layers btw 🤔

[raven summit]

I have over 300 items that I can pick up, some I can put on others. I want the item to not collide with the other item that is equipped.

[timid dove]

this is very simple to do with layers...

you would only need two layers

[raven summit]

I tried this already
I created layers "item", "parentItem" and "childItem"
"item" have items that are not connected to each other
Connected items change layer to "parentItem" and "childItem"
And it works well
Unfortunately, if I have 2 objects that have an item on them they also do not collide with each other

[timid dove]

why do you need parentItem and childItem

[raven summit]

So that they don't collide with each other

[timid dove]

why not just ItemOnGround and ItemEquipped

ItemOnGround collides with itself. ItemEquipped collides with... well, nothing.

[raven summit]

I have a sword, two shields, and two spikes for the shield

I want the shield and spikes to not collide with each other if they are connected

So everything has ItemOnGround layer if is not connected
But if I add spike on both shields and change it to ItemEquipped they will not collide with each other

the shield will not collide with the spike of the other shield
The spikes will not collide between each other

[quaint birch]

I'm not sure I understand the exact requirements for what should and shouldn't collide with what. 🤔
But also, when you say "switching them would not be optimal" - do you mean performance-wise and have you actually profiled it?

[teal summit]

how do i disable push force on a rigidbody

[timid dove]

What is "push force"?

[teal summit]

like when 1 rigid body pushes another

[dim fulcrum]

How are you connecting them? I think if you instantiate a FixedJoint connecting 2 bodies, the joint has an attribute for disabling collisions between them.

[grave spindle]

I have capsules parented with a character joint, each joint is connected to the parent rigitbody

any ideas when i move a bit a capsule, it goez crazy indefinitly ?

[timid dove]

Try moving in code via physics rather than with the editor gizmos which teleport then transform

[grave spindle]

okay ty

[midnight glade]

Yoyoyo, I'm having some troubles with managing my forces.

I have my player moving around currently in my 2,5d game with these lines:

var movement = new Vector3(direction.x * HorizontalSpeed, 0f, direction.z * DepthSpeed);
var force = movement - RigidBody.velocity;
force.y = 0f;
RigidBody.AddForce(force, ForceMode.VelocityChange);

This works fine when moving around with my WASD keys, however whenever I add another force (when my player gets hit for example) then it just cancels itself out. Is there a good way to manage both movement from input as well as other forces?

This way makes it as snappy as I want my movement. I've tried adding the movement directly instead but then I get a very non-snappy movement

[timid dove]

This code is adding exactly enough force to get you to exactly whatever velocity you are prescribing here.

In other words you're just doing a roundabout way of directly assigning velocity

Since you're directly assigning velocity it's going to overwrite any other forces

The answer is to change your approach for this movement code

Snappiness is antithetical to allowing external forces, by the way

Basically you need to limit the max amount of force you can add with this code, because currently it's unlimited

[midnight glade]

Hmm I see. I'll do some experimenting

[grave spindle]

To make cables that interact well with a dynamic environment, what would be the best ?

• using Joints ? What kind of Joints ?
• how would the texture of the cable work ? stretch ? one per mesh used ?
• if the mesh used doesnt connect well (for example i issue capsule colliders), how to make it like there are connected like a real cable ?

[timid dove]

https://assetstore.unity.com/packages/tools/physics/obi-rope-55579
https://assetstore.unity.com/packages/tools/physics/filo-the-cable-simulator-133620

[grave spindle]

ty for sharing, sadly i want to make it without paying

it will not be perfect, but can make it work

[timid dove]

The easy way is a bunch of connected rigidbodies with joints

But it's not going to be great

LineRenderer to render it

[grave spindle]

okay ty

[grave spindle]

im kinda lost between the multiple types of joints

because rn im using character joint, and it looks like i get some issue with gravity, because i cannot make it go further because its stays on the groud

[grave spindle]

i got the capsule connected to the cube with a joint
the cube is itself connected to other joints.
the anchor of the character joint of the capsule is on the left.

when playing it looks like the cube isnt trying to go at the anchor, its staying a the same distance

[grave spindle]

if i move to fast using MovePosition on my player rigibody, i got the same issue

[summer timber]

Heyy.
Does anyone know if there is a Option to configured the speed of rb.AddForce?
I know that you can multiply the vector2 with a speed float however in my case that's not an Option because this increases the distance traveled.

[timid dove]

The "speed" of it is determined by the magnitude of the vector you provide and the force mode you use

It's a force, nothing else

The only result of a force is to change the object's velocity

What you said about multiplying the vector not being an option doesn't make any sense

[summer timber]

This is what I use: rb.AddForce(jumpVelocity, ForceMode2D.Impulse);

If I multiply it [rb.AddForce(jumpVelocity * speed, ForceMode2D.Impulse);] the result is that the jump is further and but necessarily "faster"

the jumpVelocity is calculated to reach a specific position, but as I said it is a bit to slow for me and I didn't find a solution that works yet.

[timid dove]

It's not ever going to be "faster". That has nothing to do with your jump force really

That's due to the gravity in your game

If you increase gravity you can have a faster jump

Everything after the initial impulse is all gravity not your jump force. Think about the physics involved and which forces are acting on the character at what times

[barren plover]

I did this like a million times wtf has happened here in the hierarchy?

I keep adding a cube named invisible guy and essentially its a small invisible platform to guide the player up the stairs

i uncheck the mesh renderer and then I go press "play" to try it out

but it keeps disapearing

I even pressed "saved" and then pressed the "play" button to test the stairs

and that cube object that will guide you upstairs disapeared again

[barren plover]

also i just restarted my pc just now and everything was deleted

[quaint birch]

everything?

[barren plover]

well except for the assets that i imported, i guess

[quaint birch]

that's not quite normal, assets don't go away by themselves

are you sure you opened the right project? and that you don't have viruses or a failing hard drive? 😐

[barren plover]

yep pretty sure everything good in that regard 😛

oh

btw this was saved too..
lol

thanks god lol

[quaint birch]

😅

well, no idea what the issue could be, sorry...

[barren plover]

is saving/loading scene different from saving/loading the project?? as i understand it this might be the case from the quick search i did on some youtube videos

[quaint birch]

save project is save all

save scene may not save all other assets, but they are saved when you initially create them, so they wouldn't go away

[barren plover]

i think i accidentally just fixed it somehow

[full briar]

My game is stuttering very badly w/ movement and camera, and it's not because of my framerate because im getting 300+ framerate, I also only have 40k tri's and very few models, can someone please help me with this?

[golden olive]

I have the same problem and I really want to find a solution 😭

[quaint birch]

what's stuttering? video or it didn't happen

@full briar @golden olive my guess - camera is not updated in LateUpdate of physics aren't done in FixedUpdate 🤷‍♂️

[golden olive]

Alright, I will try that 👍🏻

[full briar]

Physics are done in FixedUpdate, the only fix I've sound so far is settings the Time Step to 0.001, but that's really bad practice and ruins my scripts that use Time.DeltaTime. The camera is updated with LateUpdate, and I am using CinemachineBrain for making some noise, and a CinemachineVirtualCamera on the main camera.

[shrewd umbra]

any idea why my player jumps when i let go of the movement keys?

its only when its up and down slopes

[quaint birch]

why would it ruin your scripts that use Time.deltaTime?
also, sounds like you don't have interpolation enabled on rigidbodies or something like that

[full briar]

I have interpolation enabled, also since Time Step is the time between physic updates that means going from 0.02, to 0.001 means almost 10x more physics calculations. That means like 10x more effort on the players computer, so since it changes the physics updates, that changes the time between frames, and thus I would have to increase the numbers multiplied by Time.Deltatime.

[full briar]

You can see it on the light on the floor, and also when i go sideways its more noticable

Then here is the code for moving around via that rigid body.

This is the player model, with the Cinemachine Brain being outside and set to LateUpdate for the camera movements.

[quaint birch]

And what object is the Light on? That one's not interpolated maybe? I'd say make physics step 0.2 and see - if problem became ridiculous, then some physics aren't interpolated (either because you move something in FixedUpdate, or because you didn't enable interpolation on some RB)

[teal summit]

how do i make it so a rigid body cannot be pushed

[scenic thunder]

I think you can tick the Kinematic property, or tweak its constraints

By the way, I have a RigidBody for my character control, and it works kinda well but for example it freezes when it's against a wall in air, instead of continuing falling, and also it clips through walls when it walk toward them. It also sinks into the ground when it encounters inclined objects. I move it by updating directly transform.positon. Does smone know how to fix that, thanks !

[teal summit]

yes however then it cancels out the collision and does not detect it.

[scenic thunder]

Ngl I don't know more, sry

[teal summit]

ok that ok.

[full briar]

I just made a whole entire new system following tutorials and it still lagged, I have an RTX 3090 so it's not my CPU or GPU. Also increasing the time step means less calculations, which means less updates so that would make it worse. Everything is interpolated, and I move the character with velocity, its just so broken for me

[timid dove]

why are you multiplying fixedDeltaTime into your velocity?

that makes no sense

[full briar]

I was playing around with it, you're supposed to multiply anything that moves by Time.DeltaTime right?

[timid dove]

it won't make things stutter but it's equivalent to just diving your velocity by a fixed number for no season

[timid dove]

no

velocity is already expressed in meters per second

you only need to multiply things that are per frame by deltaTime to turn them into per second quantities

[full briar]

ok let me change it and test it one second

[timid dove]

it's not going to fix anything to do with stuttering but it's going to make your units make sense

[full briar]

I still have no idea what the problem is then

[timid dove]

show your script

in full

[full briar]

https://hastebin.com/share/uzujisureq.csharp

[timid dove]

It may have to do with your camera tilting code

[full briar]

The smoothing part?

Here is the components

including the script

[full briar]

Yep you found it, it works. I just don't know how to fix it.

[quaint birch]

Less physics calculations should have no effect on it, if things are interpolated. That's exactly what we want to make sure with that experiment!

[full briar]

Well it was the camera, I want to fix it, and I can but that would remove the Camera Smoothness effect, which I don't know how to keep w/o it breaking.

I have to go but if anybody is willing to try and fix it that would be great.

[barren plover]

Unity is full of bugs

Im trying to save my project

sometimes it doesnt save

then i try to click " save as "

and no window will start up

sometimes i restart my computer and everything works okay and then quickly after a second it all breaks again

and i have to restart my computer everytime I make a small tiny tiny teeny change in my project (?)

very frustrating

[timid dove]

I've never seen a bug like that, buit if you can reproduce it, a bug report would be a good idea.

[bleak umbra]

is your project on a shared/sync'd folder (onedrive/dropbox/google drive) or a network drive?

[barren plover]

none of that

[bleak umbra]

what exactly does "doesn't save" mean?

maybe you did expect changes to be saved that inherently cannot be saved? why does restarting "fix" it?

[barren plover]

because then changes on my project get saved

for example i add a cube in

anyway i think i fixed it somehow by pressing pause (?)

[bleak umbra]

you cant save in playmode

[barren plover]

which doesnt make sense but okay

oh so thats why

I was on playmode the entire time

[bleak umbra]

changes made in playmode are generally reverted when you exit playmode and therefore can't be saved, exceptions are changes to assets (scriptable obejcts, materials, import settings etc)

[barren plover]

so how do u make sure to exit playmode?

i press pause

and then it takes me straight in the game

[bleak umbra]

press the play button again?

anyway, this isn't physics related. so you should maybe ask this kind of thing in #💻┃unity-talk

[barren plover]

if i press play button then this shit that i dont want happens

how do i know if im in the playmode or not?

why does it take so long to load when i press "play" button instead of "pause" ?

by pressing pause i just get into the game mode or whatever you call it much faster

but it shows a progress bar when i press play

and it causes problems where changes dont get saved

sometimes

[timid dove]

you're not "getting into the game mode" you're resuming an already paused playing game

[barren plover]

ok so thats what happens when you press pause/unpause gotcha. what happens when you press "play" then?

[timid dove]

it plays the game

[barren plover]

Ok so i've added a box colider on this yellow 'ladder'

I try to test the colider and go up, i also added a ladder script from the standard package of unity 2018

[timid dove]

don't crop your screenshots

a ladder script from the standard package of unity 2018
Nobody knows anything about this script

[barren plover]

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityStandardAssets.Characters.FirstPerson;
public class Ladder : MonoBehaviour
{

    public Transform playerController;
    bool inside = false;
    public float speed = 3f;
    public FirstPersonController player;
    public AudioSource sound;





    void Start()
    {
        player = GetComponent<FirstPersonController>();
        inside = false;


    }



    void OnTriggerEnter(Collider col)
    {

        if (col.gameObject.tag == "Ladder")
        {
            Debug.Log("TouchingLadderTrue");
            player.enabled = false;
            inside = !inside;
        }


    }

    void OnTriggerExit(Collider col)
    {

        if (col.gameObject.tag == "Ladder")
        {
            Debug.Log("TouchingLadderFalse");
            player.enabled = true;
            inside = !inside;
        }


    }

    void Update()
    {
        if (inside == true && Input.GetKey("w"))
        {
            player.transform.position += Vector3.up /
            speed * Time.deltaTime;
        }

        if (inside == true && Input.GetKey("s"))
        {
            player.transform.position += Vector3.down /
            speed * Time.deltaTime;
        }

        if (inside == true && Input.GetKey("w"))
        {
            sound.enabled = true;
            sound.loop = true;
        }
        else
        {
            sound.enabled = false;
            sound.loop = false;
        }




    }


}

[round hinge]

hi. how do you set a rigidbody's acceleration?

the only API I found is AddForce and that doesn't seem to be the right function here, since it adds to previous force

[quaint birch]

and what is acceleration? 😛

[round hinge]

the velocity of the velocity

velocity is the change-rate of the final value, and acceleration is the change-rate of the velocity

[quaint birch]

okay, sorry that was far-fetched 😅 applying force leads to acceleration is what I meant

but... there's rb.velocity which you can change directly like rb.velocity += acceleration * Time.deltaTime;

[eternal sinew]

guys the platformer effector isnt working when i press a or d towards the wall it stays stationary dosent fall what should i do?

also do i provide a screenshot or something?

[quaint birch]

provide a screenshot, yes... it should generally work

maybe you configured it in the opposite direction?

(not sure what you mean by "doesn't fall"... if I recall correctly the effector just allows you to move through things - ignores collisions from certain directions)

[round hinge]

ah gotcha. still, we don't have a set for acceleration or force, we can only add to it

[timid dove]

Adding to the velocity is precisely what acceleration is

[gentle sequoia]

Someone help pls , my obstacle isn't seen in the main camera

[timid dove]

I mean, it's probably just not in the right position

What's the z position

[eternal sinew]

please wait 1 minute

[gentle sequoia]

Oh it was -0.5 , it worked lol thanks

[timid dove]

You can look at the game window before you even press play BTW

[gentle sequoia]

How?

Oh got it

Thanks

[eternal sinew]

so when i hold a as its moving left it hands on to the wall

heres my composite and effector

the effector is supposed to remove the hanging part

no?

[quaint birch]

so you want to be going through thta collider when coming from the side?

[eternal sinew]

i want it slide down even if player moves left

not stick

[quaint birch]

so, unrelated, you don't need an effector for that, you need to fix your character controller

or... 🤔 or something else, that I can't think of right now, but shouldn't be effector related

[eternal sinew]

heres the problem in a video

i havent seen any solve for this type of stuff

where should i go

for the fix?

one fix could be that if players falling i disable movement that works

yeah its fixed

thanks

[round hinge]

i want to use the internal functionalities, not overwrite them

[timid dove]

AddForce and acceleration are the same thing is what I'm saying

The result of AddForce is a change in velocity

The definition of acceleration is change in velocity

[eternal sinew]

i think he wants it to accelerate to a certain speed maybe

add force isnt acceleration (as far as i know)

it applies a constant kinetic energy on the object

so the avg velocity is always the same

[timid dove]

AddForce is literally acceleration

Again the definition of acceleration is a change in velocity

AddForce has one effect and one effect only: change in velocity

[eternal sinew]

but dosent it set the v to a constant int

if you use add force in a car game object

the car will move at same speed

[timid dove]

no?

[eternal sinew]

it wont accelerate from 0

to 10

then 100

[timid dove]

It will if you keep adding force

[eternal sinew]

oh yeah in a for loop or update

[timid dove]

the result of any individual AddForce call is to change the velocity

[eternal sinew]

so what was that guy asking ?

that should solve it

using a for loop

or

update

[timid dove]

I think maybe he's trying to get at the idea that AddForce all gets basically added up until the physics simulation and applied at once

And maybe he wants a way to end-run around that

[eternal sinew]

I see

[round hinge]

In ForceMode.Force it adds the acceleration, divided by mass of course. Aye I learned that by hit and miss today. After each physics simulation frame, all accelerations will be 0, so AddForce is just like a setter for force[1], which is a*m , acceleration and mass

[1]: because A+0=A , so AddForce essentially sets the force when it's used the first time

If your rigidbody already has force applied to it when your code is being executed, you can apply a negative force to rb.GetAccomulatedForce() to zero it out and start over

It's still a pain that we don't have direct access to the current force and acceleration, but I think it's because rigidbody doesn't have a definition of force or acceleration internally, so everytime we use it, it converts to another internal representation

[round hinge]

This depends on the ForceMode. If you use Force, the acceleration will be force/mass, but if you set it to velocity, you'd be writing acceleration directly and ignoring the mass, so a 63 value would be directly added to velocity in the next physics update.

do note that it's considering you're not applying torque or forceAtPosition to it, because that would complicate things

[eternal sinew]

i see

[timid dove]

Well, GetAccumulatedForce kind of solves the problem no?

[grave spindle]

i have a cube with a RB and a BC
when i freeze all pos and rot of the RB, i can go through the GO

my player moves with MovePosition
if i remove the RB of the cube, it blocks the player as expected
even with no constraints on the RB of the cube, the player can sometimes go throught it

[round hinge]

Yes. Problem is solved

Thanks

[round hinge]

While I'm not sure what's causing your issue, I can say the recommended solution for what you want (for the box) is to set it to kinematic

kinematic rigidbody doesn't get affected and only affects others

[grave spindle]

the thing is i would like the player to move the cube at some point

the cube has two states : static and moveable

[round hinge]

When the cube is movable, either move it manually (it's possible to move a kinematic rigidbody manually), or toggle off its kinematic for the timespan you need it moved

[grave spindle]

can a kinematic rb be subject to gravity ?

[round hinge]

Also goes without saying that you should only manually move it once per physics frame

[round hinge]

No. It doesn't get affected by anything

[grave spindle]

so i will have to apply my own gravity each fixedupdate

and own movement

[round hinge]

If you want it to have gravity then don't use kinematic in the first place

I thought the box was supposed to be static, hence my suggestion to use kinematic

But if you want it to do get affected by physics world while in static mode, then yeah the preferred solution is freezing different axis as you're already doing

[grave spindle]

Okay ty

[gentle sequoia]

Help , my player collides the block from the top , but does not stop due to block in front of it

private void OnCollisionEnter2D(Collision2D collision)
{
// Get the Rigidbody2D component of the colliding object
Rigidbody2D collidingRigidbody = collision.gameObject.GetComponent<Rigidbody2D>();

 // Check if the colliding object has a Rigidbody2D component
 if (collidingRigidbody != null)
 {
     // Nullify the velocity in the x-direction
     collidingRigidbody.velocity = new Vector2(0f, 0f);
 }

}

wrote this to stop x velocity

[cursive sparrow]

Send screenshot of the inspector.

[fossil tangle]

How do you reset the forces on a Joint? Or keep them at zero?

I need to move a compound (multiple RBs, multiple compound-Colliders) physics object instantly.

• If I move it using RB.position: Unity generates a huge force on all the joints
• If I set it kinematic, move it using RB, set it non-kinematic: Unity generates a huge force
• If I set it kinematic, move it using RB, run Physics.Simulate for several seconds, set it non-kinematic: Unity generates a huge force
• If I set it kinematic, move it using RB, wait for a few seconds, set it non-kinematic: Unity does NOT generate any forces

The annoying thing here: Unity physics is (apparently) dependent on the frame-ticking - isKinematic isn't honored until/unless real-time frames advance.

(I believe this is a known-design-problem with Physics since ... forever: isKinematic isn't real, it's an 'indicator' that is sampled by the physics engine, and used to update internal physics state at the moment its sampled, so that cahnging it on/off/on/off/on has literally zero effect (since no samples took place) - but changing it, waiting a frame/several, has effect (since it got sampled)

(but presumably there's an elegant way around this?)

It's acting as though "isKinematic" won't be sampled direclty by the physics engine, but instead is sampled by some Unity internal code that runs in FixedUpdate ... somwhere. (I'm extrapolating here based on the knowledge that the only real difference between Physics.Simulate and general ticking is that ticking runs FixedUpdate callbacks and Simualte does not)

[fossil tangle]

... testing shows that: Physics.Simulate refuses to process/remove 'accumulated forces' on RigidBodies. Currently I'm testing "what if I take every rigidbody, and add a net force that's the opposite of its current force?" before setitng it back to non-kinematic.

[timid dove]

You probably know this already but if not, this exists nowadays which will make your life easier: https://docs.unity3d.com/ScriptReference/Rigidbody.GetAccumulatedForce.html

another brute force kind of option may simply be storing all the object's relative positions, velocities, rotations, angularVelocities and restoring them manually after the move

[fossil tangle]

Doesn't work. I end up with:

1. set kinematic = false
2. set RB.accumulated forces == 0 (by applying inverse of last-known accumulated force) (checked via Debug.Log)
3. ... Unity reports net forces on the Joints

So I'm back to squre one: How do you reset the forces on joints? Even removing the forces on all RBs has ... no effect

... OR: is there a way to mark Joints as kinematic? Because my core problem with joints is that Unity is generatnig forces on them when both ends of the joint are kinematic RBs.

[fossil tangle]

velocity etc are all zero already

[timid dove]

The fundamental annoyance of unity physics is that none of the components simply have an enabled property

[fossil tangle]

But these forces on joints (that are created purely as a side effect of moving the parent RB) are non-zero, and I can't see a way to directly zero-out the 'force on joint').

[timid dove]

Maybe destroy and recreate the joints? 😭

[fossil tangle]

LOL yeah OK that might work

super hacky but ... I think I have all the info to do it safely

[timid dove]

Super annoying because there's no good way to properly copy all the properties doing that

[fossil tangle]

I already have code that copies Joint properties (just a long class of copy/paste code to store everythign into a serializable equiv of Joint) to fix issues in the inspector / configuring joints from scripts.

[timid dove]

oh nice

[fossil tangle]

drum-roll please ... let's see if this works...

Ugh. Fails (although this can be solved I think), because of the other super annoying bug in Unity Physics: OnJointBreak is just trash

(OnJointBreak is apparently being called for the old - destroyed! - joint)

(although obviously there's no way to know, since Unity won't allow anyone to know which joint broke)

[fossil tangle]

OK thanks to @timid dove 's idea to destroy-and-rebuild the Joint eevery time ... this seems to work.

What happens:

1. set isKinematic=true
2. Modify the RBs
3. Verify that all RBs have force == 0 and velocity == 0
4. Cry. Because Unity Physics sucks and ignores the "isKinematic" field for processing Joints
5. Set all Joints to be infinitely strong
6. Add a custom component to every joint that had a break threshold - this is literally "WorkaroundUnityCantImplementBreakableJointsCorrectly.cs"
7. Set the custom component to "ignore joint forces for N seconds"
8. set isKinematic=false
9. watch Unity generate a 160N upwards force on the joint ... for no apparent reason ... then a 250N downwards force on the joint ... for no apparent reason
10. watch Unity drop the object ont the ground ..... then rapidly reduce the joint-forces to 12N (which is ... within what I'd epxect given the joint connects two masses of 1kg each)

...what I'm not 100% sure of: were the joint-forces created (but this would still be incorrect) as a side-effect of the object falling (it falls literally 10cm after I re-enable the RBs - so "160N up, then 250N down" really doesn't make sense) ... or were they (also incorrect by Unity) generated as a side-effect of teleporting the RBs (this appears likely: the distance travelled over the timestep would give something in the range of 100's of N)

[errant ocean]

cant use character controller as cloth collider?

[white grotto]

Hey, does anyone know a way to limit the distance between rigidbodies when using a Spring Joint? Seems weird that there isn't a cap on how distant the rigidbodies can be

[ionic matrix]

Hey guys does anyone know why my Physics.CheckSphere is acting as a collider? It's bumping up my player height off the floor making it float. I know the issue is with the Physics.CheckSphere because if I disable it my player is not floating anymore.

Any ideas?

https://gyazo.com/75f96d680a1471cd094072f528b15346

[timid dove]

your CheckSphere call is definitely not acting as a collider

something else is the problem

note that CharacterController has a Skin Width

if I disable it my player is not floating anymore.
It's probably due to your code doing something different when isGrounded is false then

I bet you'd get the same issue if you wrote this instead:
character.isGrounded = true;

[ionic matrix]

Hey thx, changing this value to the lowest possible fixed the issue

[blazing acorn]

why is my item just phasing through the floor when i drop it?

[timid dove]

tunneling

[blazing acorn]

whats that

[timid dove]

https://gamedev.stackexchange.com/a/192403

fixes are:

• turn on continuous collision detection for the moving objects
• make the colliders larger/thicker
• make the objects move more slowly
• reduce the fixed timestep
• do your own manual box/raycasting in FixedUpdate

[mint valley]

help pls collision not working

no

its enable

[timid dove]

how are you moving your object

doesn't look like you're moving it via physics

looks like you're probably moving it via the Transform, which will ignore physics.

[mint valley]

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class movePlayer : MonoBehaviour
{
    private Rigidbody rb;
    public float speed = 0.5f;
    private Vector3 moveVector;

    void Awake()
    {
        rb = GetComponent<Rigidbody>();
    }

    void Update()
    {
        moveVector.x = Input.GetAxis("Horizontal");
        moveVector.z = Input.GetAxis("Vertical");
        rb.MovePosition(rb.position + moveVector * speed * Time.deltaTime);
    }
}

[timid dove]

ok yeah you're using MovePosition

which also ignores collisions

[mint valley]

oh

[timid dove]

you're also doing it in Update

which is incorrect

MovePosition should only be used in FixedUpdate

doing it in Update will lead to weirdness/jittering.

you should just set the velocity instead

    void Update()
    {
        moveVector.x = Input.GetAxis("Horizontal");
        moveVector.z = Input.GetAxis("Vertical");
        rb.velocity = moveVector * speed;
    }

simpler and will work better

[mint valley]

[timid dove]

Looks like it's working as coded

I presume you want gravity though?

[mint valley]

yes

[timid dove]

If you want realistic physics you should be using forces

For example

    void FixedUpdate()
    {
        moveVector.x = Input.GetAxis("Horizontal");
        moveVector.z = Input.GetAxis("Vertical");
        rb.AddForce(moveVector * forceMultiplier);
    }```

[mint valley]

oh

i cant do this script

i noob

[mint valley]

can you do this full?

[timid dove]

it's pretty much full

[mint valley]

well, if you just write it down, it won't work

[timid dove]

What's not working for you

[oak wave]

I am having this weird issue where colliders just slow my player down instead of acting as a barrier

[timid dove]

What's the picture supposed to be showing us?

Explain how your objects are set up and how your player is moving

[oak wave]

The player just phases through a tree that has box colliders attached to it and the player has a box collider too, the player is moving VIA rigid body

Like it slows down the player

doesn't collide

[timid dove]

Show the code for the player movement

And show the inspectors for the objects

[oak wave]

using UnityEngine;

public class PlayerMovement : MonoBehaviour
{
    public float moveSpeed = 5f;
    public float jumpForce = 10f;
    public float fallMultiplier = 2.5f;

    private Rigidbody rb;
    private Vector3 moveDirection;

    private void Start()
    {
        rb = GetComponent<Rigidbody>();
    }

    private void Update()
    {
        float horizontalInput = Input.GetAxis("Horizontal");
        float verticalInput = Input.GetAxis("Vertical");

        moveDirection = new Vector3(horizontalInput, 0f, verticalInput).normalized;

        if (Input.GetKeyDown(KeyCode.Space) && IsGrounded())
        {
            rb.AddForce(Vector3.up * jumpForce, ForceMode.Impulse);
        }

        if (rb.velocity.y < 0)
        {
            rb.velocity += Vector3.up * Physics.gravity.y * (fallMultiplier - 1) * Time.deltaTime;
        }
    }

    private void FixedUpdate()
    {
        rb.MovePosition(rb.position + transform.TransformDirection(moveDirection) * moveSpeed * Time.fixedDeltaTime);
        AlignWithGround();
    }

    private bool IsGrounded()
    {
        RaycastHit hit;
        float distance = 1.1f;
        Vector3 offset = new Vector3(0f, 0.1f, 0f);

        if (Physics.Raycast(transform.position + offset, Vector3.down, out hit, distance))
        {
            return true;
        }

        return false;
    }

    private void AlignWithGround()
    {
        RaycastHit hit;
        if (Physics.Raycast(transform.position, Vector3.down, out hit, 1.5f))
        {
            Vector3 groundNormal = hit.normal;
            Quaternion targetRotation = Quaternion.FromToRotation(transform.up, groundNormal) * transform.rotation;
            transform.rotation = Quaternion.Slerp(transform.rotation, targetRotation, 10f * Time.deltaTime);
        }
    }
}

[oak wave]

I found a fix but if you are still willing I'd like to see how you'd fix it to see if it's simpler/more effective

[timid dove]

You're moving with MovePosition which doesn't respect colliders

You should move with velocity or forces

There's no reason to use MovePosition for what you're doing, you can just set the velocity

[oak wave]

Thanks

[echo geyser]

Its free and open source!
https://github.com/Ali10555/FakeRopeSimulation

[inner thistle]

What's the difference between rope simulation and fake rope simulation?

[timid dove]

Well instead of creating a real rope in the computer this one only creates a fake rope

[fossil tangle]

Does anyone know of documentation for RigidBody.position, Colliders, Center-of-Mass, and how they interact together? I'm getting fed up of all the bugs in Unity core physics, all the magic assumptions and calculations that are missing from the main Unity docs (or are simply wrong). I'm playing whac-a-mole to reverse engineer the 'actual, real, docs', but it's painstaking and slow

e.g. moving an RB that has child RB's - Unity does "Crazy Random Stuff(TM)" that sometimes (about 30% of the time) is what you would expect form the docs ... but the rest of the time it just sets CoMs literally ten meters away, explodes the sim, etc.

[lyric remnant]

I am having trouble with my player in my first person game going through walls when its not supposed to

Player settings

Wall settings

[fossil tangle]

The number of bugs in Unity's RigidBody.position code is just astounding.

• iskinematic is simply not implemented correctly - some actions that happen while kinematic get "remembered" by Unity when objects go non-kinematic
• ...e.g.: Joints get phantom forces (up to 3,000 N) if their RBs do anything while kinematic, even if you zero all the forces on the RBs, the RBs all had 0 velocity, and none of the RBs changed relative position
• ... e.g. rigidbody.position is overwritten by Unity if set while kinematic - it gets some kind of merged value partway between the correct value and the old value
• Moving via rb.position randomly causes Non-zero mass RB's to explode if they have no collider children
• rigidbody.automaticCenterOfMass requires another (undocumented) method if you set it - otherwise physics explodes

This from the current docs is a pure lie: "If isKinematic is enabled, Forces, collisions or joints will not affect the rigidbody anymore"

[lyric remnant]

Its weird because the ground has the exact same settings as the wall and it works fine

[bleak umbra]

You can try looking at the underlying SDK docs for more info. https://docs.nvidia.com/gameworks/content/gameworkslibrary/physx/guide/Manual/Index.html

[fossil tangle]

I believe all the isssues are in Unity, not PhysX. Unity's interpretation layer that customizes how PhysX works is the bizarre thing that acts unpredictably - and PhyX has no notion of things like "Transform", or any other Unity APIs right?

[bleak umbra]

Speculation

Seems like all your issues occur in situations that aren’t using rigid bodies as intended

[fossil tangle]

"As intended" would be great if you could refer me to docs on exactly what is intendede

All I can find from Unity officially is vague handwaving of "you'll have to work harder for more complex situations"

[bleak umbra]

Suppose you have to use common sense in that one. Messing with a rb while using joints is clearly going to mess up the simulation for example

also changing from kinematic on/off during the sim is obviously going to have some issues

[fossil tangle]

I guess the TL;DR is: "when you have mutiple RBs, and multiple joints, and Unity's center-of-mass calcs go wrong after a time ... and you can manually set the CoM correctly, or manually set the transfom/RB positions correctly - and that 100% always fixes Unity ... how do you do the same thing in script corretly?"

[bleak umbra]

those are all situations that would need a bunch of checking to solve ‘correctly’ and that would be slow.

[fossil tangle]

Sure, slow is fine - right now I'd be happy with 'slow but correct'.

I can seem to get Unity to get 4 out of 5 things correct - I can change which is the one that's failing, but can't seem to get all 5 at once

[bleak umbra]

Maybe by doing it over multiple simulation frames. Giving the system an opportunity to incrementally deal with your fix.

[fossil tangle]

That's where the CoM problems bit me - when Unity loses the CoM you don't have multiple frames, you have to act instantly, because otherwise Unity flings things around

(up until that point I was using mulitple frames to let things settle, and freezing some RBs completely, freezing joints completely, etc)

[bleak umbra]

it seems to me that fixing physics is always a futile effort, so if fixes aren’t trivial, i’d abandon the feature

[fossil tangle]

In editor, if I hit Pause, then toggle "automatic CoM" off then on again, then UnPause ... all is fine. But trying to recreate the same effect in ode is killing me 😄

[bleak umbra]

That’s equivalent of using multiple sim frames

[fossil tangle]

(according to the docs: that shouldn't have an effect, becaue once CoM is on its supposed to stay auto-updated forever)

[bleak umbra]

maybe you can ‘catch’ it after being flung and bring it back

[fossil tangle]

That's where I got into all the pain of RB.position being unrpedictable

[bleak umbra]

😝

[fossil tangle]

It seems Unity won't allow you to re-position RBs if they're in a hierarchy

(it sometimes works, but often doesn't, and Unty usually resets things back to a state from multple frames earlier)

(I have no idea why it would do that)

[bleak umbra]

rb shouldn’t be in a hierarchy

[fossil tangle]

"shouldn't" is great for toy sims, it doesn't fly for big games. Unless "shouldn't" is "cannot" - but unity staff never say it's wrong

[bleak umbra]

rb ignore the hierarchy

[fossil tangle]

I have considered converting everything to no hierarchy - as far as I can see this means breaking most of the rest of Unity though. All the API methods will be gone (Find, GetComponentsInChildren, etc), all the 3rd party code will break, etc.

[bleak umbra]

If you nest them or move them via parents, you’ll have issues

[fossil tangle]

I know!

If I could find an official statement from Unity "our code for RBs is knwon broken for hierarchies, sorry, we broke the core Unity archirecture on this one, just don't do it, we're not supporting it" -- fine. But I can't find that anywhere.

[bleak umbra]

It’s not broken. Rb fundamentally cannot be in a hierarchy

[lyric remnant]

so nobodys gonna help me

[fossil tangle]

Instead I find references to "it's tricky" and "it's harder" and "it's less obvious" -- but no concrete statements on what/why

[bleak umbra]

you cannot solve forces and collisions effectively (with minimal iterations) if you have to respect hierarchical relationships

it’s tricky because it can work sometimes if you know exactly what you are doing but on principle, each force simulated rb must have a static parent that is not a rb.

You can use the hierarchy to organize them, but you cannot touch the transforms

[fossil tangle]

" it can work sometimes if you know exactly what you are doing" <-- I think this is what I have a lot of examples of now, from my own scenes. It's just ... I have no info on what I'm not allowed to do with them, and so things keep going great then suddenly ... not great.

[lyric remnant]

Thanks guys

[bleak umbra]

You are not allowed to touch the transforms

[fossil tangle]

FYI: my core case works 100% for moving, using transforms, reparenting (mulitple times), using physics, etc ... until you remove ssome RB's from the hierarchy. Then Things Go Werd.

So ... if I get you corretly:

1. connect all RBs via joints
2. throw them into transform hierarchy
3. but never again move the transforms in that hierarchy <-- .position, .rotation, etc
4. should be OK?

Additionally, by trial and error:

1. If I need to move 'everything' (e.g. to recenter in game-world, or e.g. to move to respawn location) -- I've found that Joints go haywire if I use RB.position (I have to destroy all joints, then recreate them immediately precisely as they were before being destroyed)
2. If I need to move 'everything' ... I'll have to do it by teleporting just one 'main' RB that is connected to all the others by joints ... and only via RB.position (since: mustn't touch the transform APIs)
   ?

If that all works ... that would be great, although I'm 95% confident I've obeyed all the above at least once and something still went BOOM - but if you think that list looks correct I'll try writing everything again from scratch and verifying if it does (maybe during my trial-and-error I got one thing differnet from the above, and didn't realise)

[lyric remnant]

Let me know if anyone else decides not to completely ignore me 🙂

[bleak umbra]

Show your code and scene

[bleak umbra]

Seems reasonable

[fossil tangle]

Attaching inspectors doesn't much help without the rest - scene, code, etc. Quick glance suggests your wall is too high and you can walk under it (but without seeing the scene that could be wrong)

[bleak umbra]

Experience here often is that the asker shows exactly the bits of their setup that don’t contain the issue.

[lyric remnant]

using System.Collections.Generic;
using Unity.VisualScripting;
using UnityEngine;

public class PlayerMovement : MonoBehaviour
{
    public float playerSpeed;
    public float horizontalInput;
    public float verticalInput;
    public float yRotation;
    public float jumpForce;
    public float playerHealth;
    public bool isOnGround;
    public Rigidbody rb;
    public GameObject playerCam;
    public GameObject ground;

    // Start is called before the first frame update
    void Start()
    {
        rb = GetComponent<Rigidbody>();

        playerHealth = 10f;
    }

    // Update is called once per frame
    void Update()
    {
        horizontalInput = Input.GetAxis("Horizontal");
        verticalInput = Input.GetAxis("Vertical");

        transform.Translate(Vector3.forward * Time.deltaTime * playerSpeed * verticalInput);
        transform.Translate(Vector3.right * playerSpeed * horizontalInput * Time.deltaTime);


        yRotation = playerCam.transform.eulerAngles.y;
        transform.eulerAngles = new Vector3(transform.eulerAngles.x, yRotation, transform.eulerAngles.z);

        if (Input.GetKey(KeyCode.Space) && isOnGround)
        {
            rb.AddForce(Vector3.up * jumpForce);
        }
    }

    private void FixedUpdate()
    {
        
    }

    void OnCollisionEnter(Collision collision)
    {
        if (collision.gameObject == ground)
        {
            isOnGround = true;
        }
    }

    private void OnCollisionExit(Collision collision)
    {
        if (collision.gameObject == ground && isOnGround) 
        {
            isOnGround = false;
        }
    }
}```

@bleak umbra

[bleak umbra]

You aren’t using physics/forces to move the character

[lyric remnant]

how do I do that

[bleak umbra]

rigidbody.AddForce()

[lyric remnant]

I changed it to this but its not working

rb.AddForce(transform.right * playerSpeed * horizontalInput * Time.deltaTime);```

oh never mind its working the player speed was just as slow as can be

[bleak umbra]

You should read the docs some

whichever way you slice it, a character controller is a hard problem.

[lyric remnant]

thanks for your help

[lyric remnant]

it took an hour but I finally finished movement 💀

[dark wren]

Is there a way to detect forceful collisions? I'd like to do a little screenshake whenever my character collides especially hard with something

[timid dove]

Sure OnCollisionEnter provides a Collision struct with lots of information about the collision

[zinc terrace]

why the wheels colliders are a bit forward of the mesh when i play it?

it doesnt roll up 😭

[cursive sparrow]

Given that I have linear drag = 25, and apply a force to an object using AddForce with Impulse, how would I calculate the time it takes for the object to go back to it's initial velocity, in seconds? I.E, how to calculate when the object stops after an impulse.

(This is because I'm using add force for knockback, and I'd like the player to be invulnerable to damage while being knockbacked)

[quick ridge]

How do I make wires

one that I can grab-ish

[blazing acorn]

to edit this meshes convex collider would i have to do it in blender or can i edit it in unity?

[timid dove]

You can edit meshes with #🛠️┃probuilder or Blender. Note you can't separately edit a mesh Collider. You'd create a copy of the mesh for a custom collider

[cursive sparrow]

bump

[lyric cape]

hey guys?

i need help with a mesh collider...

i import an model as fbx and put it 2x in the scene...
added both the rigidbody and mesh collider...

but the mesh collider dont work...they fall from the terrain...
if iam lock the Y axes to try the collision between them, then I can go through them...

so...how i can fix it? (its an playerObject, so the convex mode isnt usefull)

[quaint birch]

mesh colliders are sad and have various limitations... can't you use something more primitive?

[lyric cape]

well sadly no 😦 its an open world 3D Sci-Fi game...so i need a collider who use the correktly body as collider 😦

do you have any ideas?

[quaint birch]

is it a convex mesh collider?

[quaint birch]

I don't quite remember the rules about what collides with what... concave mesh colliders don't collide with other mesh colliders... convex ones might be fine
so, first check if yours is convex and mark it as such if not and try again
also keep in mind that mesh colliders are somewhat expensive

[lyric cape]

i said before...
i cant use convex mode bcs then isnt used the detail skin

convex mode is just usefull for stones or other objects...but not for player or enemy objects

[quaint birch]

yeah, so no solution, the physics engine doesn't support concave colliding with anything but primitive and even then it's maybe not a great idea

normally people just use a close-enough shape based of a few primitive colliders for players/enemies

[lyric cape]

mhh 😦 okk thank you

[blazing acorn]

why is my imported from blender collision model offset like this?

in blender its just on the world origin

[errant ocean]

no edit bounding volume on my second capsule collider?

[quick ridge]

how to make nice movable wires

[fossil tangle]

Actually ... I'm not convinced this is necessary. I think I may have a simpler problem with Unity physics that is confusing the output of RB.position etc.

Paring my project back:

1. Object "root" has an RB { mass = 0, CoM = auto, gravity = true, kinematic = false}
2. 2 x objects "child1", "child2" have RBs {mass = 1, CoM = auto, gravity = true, kinematic = false, and 1-4 child colliders each}
3. In FixedUpdate, "root" does this:
4. 3.1: calculates a new position in world space
5. 3.2: removes all children (transform.setParent( null ))
6. 3.3: sets RB.position to the new world-space position chosen in 3.1 above
7. TheEnd.

Debugging shows:

• Root's position is 0,0,0 throughout
• Root's RB.position is changed at 3.3
• Root's RB.position jumps to a (stupid incorrect value close to 0,0,0) in-between the FixedUpdate frames

But ... if I additionally "destroy all joints" before doing anything then ... nothing gets corrupted.

TL;DR: looks like nested RB hierarchices might be fine iff you simply "destory all joints before doing anything" and then "recreate them immediately after doing anything".

NB: supporting that (destroy/recreate all joints) is pretty much a requirement in current Unity anyway, since the joint APIs in Unity are so badly broken/missing (OnBreakJoint, forces, etc). So ... if you're already working around the Joint problems, "destroy and recreate them all" is almost free.

... will continue testing with this in mind, and report back if it works.

[thorny isle]

does anyone know how to fix this? ive been stuck on this for so long lol

also
https://paste.ofcode.org/Gpyu9hF7uqzKX2JUKcvgnz sliding script
https://paste.ofcode.org/mxU2LDvGsfnZ6RV3XrXXPy PlayerMovement script

im not sure how to fix it , physics do be hard

[visual gale]

I have EdgeCollider2D and a PolygonCollider2D with the same shape. I want to shoot at ray from a point and find the edge intersection point. However, it grabs the poly first. I figured I would use layers, but then it gets lost:

LayerMask mask = LayerMask.GetMask("GenEdge");
eCollider.includeLayers = mask;

RaycastHit2D[] results = new RaycastHit2D[2];
ContactFilter2D cf = new ContactFilter2D();
cf.SetLayerMask(mask);
Physics2D.Raycast(Vector2.zero, p, cf, results);

But no results are returned. If I comment out the includeLayers assignment, both results are returned. What's goin on?

[visual gale]

I'm going bonkers.

This makes no sense. I have two colliders, one has a mask and one does not. Passing mask into contact filter or any raycast* variant filters both out.

[signal island]

not sure what you're trying to achieve, but after looking at your code, it looks like you aren't checking if the player is grounded before you slide

private void Slide()
{
    if(!pm.grounded)
    {
        return;
    }
  //rest of code here
}```

put that in ur slide function

whatever handles sliding

[thorny isle]

Yeah but then I won't be able to slide after a jump , someone told me to just set the playerobj and orientation position to 000

[signal island]

i see

[thorny isle]

Yeah , I will try that and see if it works

It might work idek

[exotic coyote]

Are there any hidden black magic tricks to make collisions feel better with rigidbodies,like some basic rules to follow.Currently it feels like my car is hitting a wet noodle that doesent move

[timid dove]

Step one make sure your objects are actually moving via physics and not by teleportation with the Transform

[exotic coyote]

Yea already got that area covered

Only using addforce and addtorque

[fossil tangle]

Is there a checklist/guide somewhere that lists "all the things we commonly forget/get wrong with Unity physics?" -- I think I know most of them 🙂 but it would be handy to have something I could consult when things go wrong, written from a perspective of "if you already know what you're doing, have solved these problems before - but just need a reminder of common mistakes"

[errant ocean]

why are my cloth vertecies not showing up when editing cloth constraints?

[rapid knoll]

hey im a complete beginner and im tryin to let the ball move to the platform in the right to let them collide and experiment with it. the problem is that if i simulate it my ball gets stuck at this position and is like shaking, bugging and is stuck and will not move further until i tab out and tab in again which does not make any sense does it? 😭

[fossil tangle]

RigidBody.position -- I hate it.

bool go = false;
public void FixedUpdate()
{
if( go )
 GetComponent<RigidBody>().position = Vector3.one;
}

... has the effect:

1. Body resting on the ground, all is fine, nothing happens. Transform is at (0, 0.5, 0 )
2. Enable 'go'...
3. Body now sinks slowly, at a rate of 0.4 meters / FixedUpdate, through the floor.
4. RB.position is reported as being (1.0, 1.0, 1.0).
5. Transform.position is reported as gradually getting lower and lower.

W. T. F?

Why is RigidBody.position so bad?

(FixedUpdate is default - so IIRC 0.02 seconds/frame. So it's sinking at 8cm / second. Why?)

It seems ... setting RB.position without also manually setting transform.position ... gives RB's velocity ... which even if you continuously set RB.position to the same value, Unity's crap physics ALSO runs the 'you have a velocity, so I'm going to move you'.

There is no velocity, Unity.

And then re-run exact same scene, exact same params, and ... it doesn't sink at all.

[timid dove]

I think this actually makes sense.
There's this to contend with:

• FixedUpdate runs, setting the position
• The physics simulation starts
• inside the physics sim, graivty is applied to all objects, increasing their vertical velocity downwards
• objects are all moved according to their velocity
• physics sim ends
• Your object is no longer at 0.5

So this actually makes total sense IMO

because the velocity is accelerating each frame

so each time, by the time you are rendering things, the object will have moved down by a single frame's worth of distance

which keeps increasing because the object is accelerating downwards

setting rb.position doesn't modify the velocity

[fossil tangle]

That would make more sense if ... re-running the same scene a second time it doesn't happen.

But I agree it would make sense if the rule was "if you want to set RB.position, you must ALSO always manually reset the RB.velocity, because otherwise any velocity you'd acquired previously would be carried along with you and change your position".

But I also don't understand why the position INCREASES each frame

note that the velocity does NOT increase

it's not accelerating down, just... drifting at constant velocity

[timid dove]

because it's accelerating. Why wouldn't the velocity increase?

[fossil tangle]

Because I left it for 10+ seconds and it was still falling at same rate

[timid dove]

Eventually it will reach equilibrium if there is drag

[fossil tangle]

But I am resetting it to 1.0 each frame.

So why does it get 0.1 lower each time:

1.0, .9, .8, .7, .6

when Im resetting position to 1.0 each time?

[timid dove]

it should accelerate. I guess I'd like to see this in action

[fossil tangle]

Well. As noted: I hit stop, then play again, and ... it didn't happen 😄

Didn't move at all

[quaint birch]

because more and more gravity?

[timid dove]

or perhaps it has picked up some initial velocity somehow (collided with something?) and is not accelerating?

[quaint birch]

okay, repro it, and then we can talk 😄

[fossil tangle]

Now it's locked at 1.0 - where I've set the RB position - suspended above the ground

(which is what I expected first time)

(but thanks for the point about drag - it's a good point, I should remove all drag while testing this stuff as it just confuses things otherwise)

Trying to make small repros here, I've got this --- which I expected to do:

1. instantiates 2nd object
2. places it in midair above 1st object

But in fact does:

1. instantiates 2nd object
2. places it in the scene 1 meter to the side of the original prefab it was instantiated from

public class AccumulatingRigidBody : MonoBehaviour
{
    public Rigidbody prefab;

    [ContextMenu( "Add wing on top" )]
    public void Menu_AddWing()
    {
        var wing = Instantiate( prefab );
        wing.transform.SetParent( transform, true );
        
        delayedCalls.Add( rigidbody1 =>
        {
            Debug.Log( "Setting RB.position of prefab = "+wing.name+" to be above RB = "+rigidbody1.name+ "-- i.e. "+(rigidbody1.position + 3f * Vector3.up) );
            wing.position = rigidbody1.position + 3f * Vector3.up;
        } );
    }

    private List<Action<Rigidbody>> delayedCalls = new List<Action<Rigidbody>>();
    public void FixedUpdate()
    {

        if( delayedCalls.Count > 0 )
        {
            Debug.Log( "Starting FixedUpdate calls" );
            foreach( var c in delayedCalls )
                c( GetComponent<Rigidbody>() );

            delayedCalls.Clear();
            Debug.Log( "Finished FixedUpdate" );
        }
    }
}

Hmm. So ... simple experiments suggest:

1. calling RB.position on an RB that became nested in that same frame is just ...undefined behaviour. Unity can do the same thing 10 times in a row, then something bizarre instead.
2. calling RB.position on a plain RB, waiting one frame, then nesting it ... works perfectly

the problem being 'undefined behaviour' -- if it were consistent (even: consistently failing) I'd not have walked into so many deadends.

[quaint birch]

generally nesting RBs tends to be imperfect, unless they're kinematic and that too may lead to some weirdness

[fossil tangle]

From earlier conversations: "tends to be imperfect" isn't helpful, there's many people saying that and waving their hands vaguely. I'm looking for actual concrete statements about what works, what doesn't.

(which I cannot find any documentation from Unity staff on, anywhere 😦 )

[quaint birch]

fair point... sorry, I've not done enough lately to be less vague... I know I just usually found ways to not nest things... and I recall it somewhat working for what I needed with kinematic RBs

[fossil tangle]

yeah, sadly I'm waaaaay beyond being able to simple say 'dont nest'

[rapid knoll]

that was so complex written that i dont even know if you wanted or tried to help me or if this is another subject

tbh

[rapid knoll]

i guess ill try that then

thanks

[rapid knoll]

also i really do like the explanation so thanks alot but honestly it still seems to complex for me 😭

[fossil tangle]

New update on RB.position and transform hierarchies of multiple RBs....

I've refactored my code enough that I can afford to have a hierarchy where:

• the top-level transform DOES NOT have an RB, only the children have RBs
• all the children are connected to each other / their siblings via joints (this was always the case)

With this in place, the following works fine:

1. You teleport a hierarchy of RBs not by using RB.position (it has way too many problems of its own), but instead by transform.position on the root transform (which, note: does not have an RB any more)
2. Caveat: Unity's joints have their stupid internal state that's private, so you still have to delete all joints and recreate them exactly the same as they were after teleporting

i.e. I gave up, Unity Physics defeated me. It just sucks too much :). But the compromise of "all Unity code operates on the root transfrom (no RB), all UnityPhysics code operates on the child RB's" seems to be working so far.

Tests have shown that this will randomly 'keep working' or 'go insane' (no way of knowing which - I cannot find any way of predicting, it's just some inherently unstable thing in Unity's code -- it feels like a bug, because it's deterministcally random, so I think it's something messed-up in Unity's internal calcs) the moment anyone inserts another RB as a child of one of the child RBs (i.e. someone adds a 'grandchild' RB). I've looked through a few and I think (fingers crossed) I'll be able to detect those cases and throw Exceptions, with a note to use my custom API call which does the same except moves the grandchild to be a sibling, to workaround Unity's problems with RB.position.

...I've now got one problem left :). Hoping someone has an easy solution to this:

When the root object has non-RB children as well as RB-children ... any movement of the RB's leaves the non-RB's floating in the air. This makes sense: since the root has no RB, there's no direct way for the child RB's to drag the transform of the parent along with them.

It would be theoretically possible to create RBs for everything - but that will increase the number of physics objects in-scene by thousands, for literally no reason (we don't want them to be RBs, we dont want them to participate in physics - they're just passive items along for the ride).

... I'm wondering if there's an easy thing to do that e.g. each frame in FixedUpdate read "change in RB.position since last update" and then apply that change to all non-RB children? Maybe it should delay the change "until next Update() call" so that renderer animates them smoothly - or maybe it shuold happen instantly inside FixedUpdate so that the physics and non-physics stuff moves together?

[quick ridge]

how to make collider not interact with physical objects but can be raycasted? (for interaction purposes

seems like what ever I am doing is just making the collider inactive, which wont make raycasting it possible

I want to make the collider not become solid, if ok

[timid dove]

Make it a trigger

Or put it on a layer that doesn't interact with any other layers

Or add all layers to the exclusion list on the collider itself

Many options

[scenic niche]

Hello, so I was trying to make a game where truck runs off and follows a certain path

and i wrote this code to calculate the steer angle of wheel colliders

        Vector3 ourPos = transform.forward;

        float newSteer = Vector3.SignedAngle(nodeRelP, ourPos, Vector3.forward);
        Debug.Log(newSteer);
        FL.steerAngle = newSteer;
        FR.steerAngle = newSteer;

        FL.motorTorque = torque;
        FR.motorTorque = torque;```

i am using signed angle on z axis to calculate the angle relative to the trucks rigidbody

but after somer time, the wheel collider is frequenting between -ve and +ve values

What am I doing wrong?

[timid dove]

Why do you have vectors called "pos" that are actually direction vectors?

and why are you using Vector3.forward as the SignedAngle axis? Is that always true?

[scenic niche]

i mean its a cross product between two vectors a and b with the axis defined right?

[timid dove]

it's not a cross product, Vector3.Cross is the cross product

[scenic niche]

so i am taking the relative position vector, the forward vector and the z axis

[timid dove]

why the forwrad vector

Is your car always facing the same direction in the world or something? Can you draw a picture here?

[scenic niche]

docs said to follow left hand rule to find the angle relative to axis

[timid dove]

Did you actually want transform.forward?

because Vector3.forward is just (0, 0, 1)

[scenic niche]

i see, that can be a problem, and no, the car rotates in the world, freely

so i need to make the forward relative right?

[timid dove]

then you can't just blindly use Vector3.forward

[timid dove]

transform.forward will be the forward direction of the car at the current moment, if that's what you want

or at least carTransform.forward

[scenic niche]

yea, will check and do the maths again

thanks

[quick ridge]

trigger is ok

are there consequences to using triggers? also I cant change it to a different layer because I need it for the code

[timid dove]

of course there's consequences, else there'd be no point in doing it

[quick ridge]

ah, I just realized, every interactable is no longer solid

maybe if I make it have ID, and if it is that id, is Trigger is not check?

[wispy patrol]

Hey guys

I have this tree:

"Top and Bottom Half" part of the tree is able to move when the player bumps into it. However, when I remove it's RigidBody, MeshFilter, and MeshCollider; and then activate both "Top Half" and "Bottom Half" game objects part of the tree (which both already have a RigidBody and MeshCollider), those two do not move at all when the player bumps into them

The physics is the same for all three

"Top Half" and "Lower Half" do move naturally, but don't move at all when the player bumps into them.

[orchid path]

I tried to rotate rigidbody towards camera's direction, but it either exceeds camera's rotation (causing erratic behavior) or it doesnt reach it. The only way to get rid of over-rotation is to have angle constraints + delayed rotation, but i was hoping for the rotation to match the camera, not be delayed.

Rotation works perfectly if I just do this:

transform.rotation = Quaternion.Euler(0, Camera.main.transform.eulerAngles.y, 0);

it doesnt overshoot, doesnt under-rotate, is not delayed.

But it stops rigidbody movement such as:

characterRigidbody.MovePosition(characterRigidbody.position + movement);
characterRigidbody.position = characterRigidbody + movement;

what can I do here?

[sand ruin]

I think this falls under physics so i was just wondering how hard is it to make a zero gravity game like your in space for VR? Like some objects floats and you can push yourself around.

[timid dove]

very easy.

Gravity is just a setting you can change to whatever you'd like, including zero

now making a good zero gravity player controller might be a little harder, but the act of removing gravity is very simple.

[sand ruin]

Wdym by player controller?

Like the movements?

[timid dove]

like a script to control your character

[celest abyss]

What are layer overrides for? They don't even work.

I set a box collider trigger to the layer I want and the code cannot get it from a physics overlap check

[timid dove]

They are for actual collision and trigger interactions with other colliders

they are not relevant for physics queries such as raycasts and overlaps

your overlap check can be used with a layer mask.

[celest abyss]

When I set the GameObject layer to my layer then set the colliders and Rigidbody to default, the object did not collide with other instances of itself.

[timid dove]

you said it was a trigger

triggers don't physically collide with anything

they only cause OnTriggerEnter/Exit events

That interaction will also depend on your layer collision matrix settings in physics settings

[celest abyss]

Sorry I meant when I set that on my non-trigger colliders

I included default and excluded my layer from them

I guess I should just move the trigger to a separate child object

[visual gale]

Can anyone help me with some math? Given point a and b where a.z > b.z, how can I find c.x where c.z is known and c.z > b.z and is along the line/ray specified by a->b?

[timid dove]

I'd probably do this:

// a Plane at the given Z coordinate, along the x/y axis
Plane p = new Plane(Vector3.forward, knownZ);
Ray r = new Ray(a, b - a); // a ray originating from a in the direction of b

p.Raycast(r, out float enter);
Vector3 c = r.GetPoint(enter);
float desiredValue = c.x;```

[visual gale]

is that better than some right triangle trigonometry?

[timid dove]

I don't think it's different from geometry/trigonometry

[visual gale]

raycast is probably a bit more expensive than that yeah?

[timid dove]

raycast is just math

this isn't a Physics raycast

it's a Plane raycast

it's just geometry

[visual gale]

fair enough

[sand ruin]

I'm making a VR puzzle game and my idea for this puzzle is that it's a handheld cube, and there is a maze inside and a little ball. The idea of it, is that you have to rotate the cube to get the ball out. It is as simple as modelling the cube and then giving both objects a rigid body and obviously make a way so you cant just grab it out, and there is obviously an exit.

[austere sluice]

Making sure, the MonoBehaviour.OnAnimatorMove() callback/event function is called during the Physics Update section of the execution order, depending on if the Animator's Update Mode is set to Animate Physics, correct?

Currently experiencing an issue where a Character Controller who uses Root Motion and whose code lives in OnAnimatorMove(), that hijacks the rigidbody's velocity (aka it just sets it outright), is not getting affected by additional forces.

[timid dove]

Sounds like you have three components all competing to move the character

CC, Rigidbody, Animator

You should pick one of the three basically

A typical approach is CC or RB movement, and then the Animator only animates child objects

[austere sluice]

Well... it's an external asset, so I don't have full control over everything. The Character Controller handles all of the Animator state and animations and such, so you could assume CC = Animator in this case and that CC controls the RB, it mostly doesn't touch the Transform, so it's RB movement for the most part other than some corner cases. Reparenting stuff is a good shout out, but considering Root Motion, how that CC takes it and modifies it, I don't think it's a valid solution in this case.

But I think I may have just come up with an idea to try, thank you.

[vague fjord]

Hellooo I'm having a little Issue I don't really know how to resolve. I need a bit of brainstorming tbh ahaha

So, I have in my scene objects like a sofa, a desk or a table with objects on top. When hit by a player they shake and play a little animation, and I want the objects on top to fly off, fall or simply jump around.

The objects on top move accordingly but the physics are not enough to make them fall or to fly arround, it's like I need to amplify the forces they receive or something (they react a bit, but they stay on the place)

The image shows the desired behaviour:

[timid dove]

If you're using an animator make sure it's animating physics

if you're doing this animation in code, make sure you're moving the objects via the Rigidbody with Velocity/MovePosition/AddForce

[vague fjord]

The table is moved with physics, but I would like the objects that are placed on top just to react to the shaking and stuff

I mean I don't know how I would script a natural behaviour

It's just decoration

[timid dove]

It should happen automatically assuming they are dynamic Rigidbodies

and that the table is properly moving with physics

[vague fjord]

So like, they just need to be hit harder or something, to react more when the table is shaken for example

I don't know If I'm explaining myself haha

[vague fjord]

Yep, they just need to be struck harder

[timid dove]

the things to adjust would be the physic material of the table and the objects

and how much the table shakes

[vague fjord]

Mhh I can try that! The thing is that I cannot play much more with the animation as then It will look ugly for the player

[timid dove]

you could always add additional forces if you wish

to the objects

[vague fjord]

mhhh maybe I can try amplify them or something

[vague fjord]

I found a way! I used the AddExplosiveForce where the central point of the explosion is the collision contact

It kinda sells the effect

[wanton moss]

Hey all, I have a hopefully simple question: I have a Player object with a RigidBody 2D and a Box Collider 2D in order to be able to push other players. However I want a separate Box Collider 2D to act as the player's hurtbox, but the issue is that if the hurtbox extends beyond the pushbox, then the RigidBody gets pushed. My question is, how can I make the Rigidbody only apply the pushing physics on the pushbox collider? I can't really use Physics.IgnoreCollision(), because I do still need to know when they collide. Basically, is there a way to have a RigidBody's physics only apply to a specific Collider2D? I have the RigidBody on the Player itself because I need it to move the sprite and whatnot.

[timid dove]

The hurtbox can be a trigger

also you can put either or both colliders on child objects on separate layers, and use layer based collision

[wanton moss]

I've been messing with layers but I can't seem to get it to work. I have the pushbox as a child on its own layer with a collider and the RigidBody, but I'm still able to pass right through it.

So what I am confused about I guess is, say I put the RigidBody on the player itself, and then have the hitbox, hurtbox, and pushbox all be children. I would put the pushboxes on their own layer, and so the pushbox doesn't interact with the hurtbox and only pushes the player when two pushboxes collide. But then, if the hit and hurtboxes are on their own layer, how would I allow those two colliders to collide without pushing the player with the RigidBody's physics? Since it seems like the Rigidbody applies to all the children colliders.

[timid dove]

if you want to detect a collision without pushing anything, you should be using a trigger collider

[wanton moss]

That works, I have been struggling to understand the Is Trigger checkbox and this just made it click, thank you!!

[pale forge]

I'm so confused why this happens

in every sample project with a tilemap and collider and rigidbody2D

they don't get this stuttering and weird behavior on collisions

am I missing something? why does my sprite re-orient on collisions

[timid dove]

Looks like you're not moving your object via the Rigidbody

[pale forge]

May I ask what you mean?

[timid dove]

you're moving the object in a way other than via the Rigidbody.

for example you're moving it via its Transform

[pale forge]

Ah yeah I am doing that. Is that what causes the stuttering?

[timid dove]

Yes, you're bypassing the physics engine entirely

and teleporting your object inside other objects

[pale forge]

Very interesting!

[timid dove]

then the physics engine has to play catchup

[pale forge]

Very interesting Is there a reason someone would want to do that?

Bypass the engine I mean

[timid dove]

Sure there's lots of reasons for lots of things

most of the time they're doing it because they don't know any better

[pale forge]

Fair enough. Would changing this also fix the issue of how it re-orients the player upon collision

[timid dove]

no because objects rotate when they collide with things at an angle

If you want to constrain the rotation, you can do so on the Rigidbody2D

[pale forge]

Maybe I’m doing this all wrong. All I’m trying to do is make it so different “things” happen when my player touches different tiles. But none of those affects are physics-based

Should I be using something else entirely

[timid dove]

That sounds like a different concern from how you're moving your player

focus on one problem at a time

[pale forge]

Okay so like in a regular platformer, when you collide with a wall, you don’t rotate, even at an angle. Are they using a different thing than rigidbody?

Or are they just restricting it as you said above

[timid dove]

#⚛️┃physics message

[pale forge]

Ahhh is that what they do? Okay noted

[timid dove]

sure, you also want to tackle the main problem here though

which is that your movement code is bypassing the physics engine

[pale forge]

Thank you! Okay so I assume you instead should do this by applying some force to the player?

[timid dove]

you can do it by applying forces, or simply setting the velocity

it depends on the nature of the movement you're trying to accomplish

[cedar apex]

Is there a way to make my character not clip through slopes or get sent flying when crouching? my box collider's Y is reduced by half, and I have raycasts for the slope, so walking on slopes and crawling on them is fine, but initiating a crouch on a slope with cause me to clip or bounce when i crawl

[timid dove]

if you're doing something inherently non-physical like resizing a collider you should make damn sure it's not going to clip through things first

use physics queries to do so if needed

e.g. boxcast/overlapbox

[distant ginkgo]

Can someone help me? I need to reproduce this physics simulation in a vertical stack without using joint Link: https://www.youtube.com/watch?v=h5BZPXj-bo8

[woeful pulsar]

I think a simple verlet integration with upward force instead of gravity would do the trick just fine

Design it in 2D. XY are defined by the physics and Z is defined by the player current position

[distant ginkgo]

Thanks

[sonic jetty]

What would be the best way to go about a Zero G velocity deceleration? Trying to make a good looking space break but it always results in a instant stop

    private void SpaceBreak() {
        Debug.Log("Slowing Velocity toward Zero");
        Debug.Log("Time: " + Time.deltaTime + "\nVelocity Normal: " + rb.velocity.normalized);
        rb.velocity -= rb.velocity.normalized * brakeDeceleration;
        rb.velocity = Vector3.ClampMagnitude(rb.velocity, 0f);
    }```

Scratch that 🤦

Got the morning brain cell energy. obv clamping it to 0 would zero it right away lol

[timid dove]

Why not just use AddForce?

Also it's "brake"

[sonic jetty]

I could but I wasn't sure whether it would go right past 0 or return to it.

and direction was another thing I was unsure about. But I guess the force value can be based on transform.down* yaxis

[timid dove]

Depends how much force you add.

For a brake you'd add force in the opposite direction as your current velocity

Which you can also use to determine how much force to apply - limit it based on the current velocity

[sonic jetty]

What would be the ideal way to find the direction of the velocity. Is that built in?

[timid dove]

rb.velocity

You're already using it

[sonic jetty]

just invert it then?

You are right, that works just the same! Though Ima still clamp magnitude because my current velocity is reading 2.479443e-07 when I break to 0

[hollow wind]

Hello!

I've discovered something that I can't find a fix for:

1. I have a GameObject that contains a SphereCollider.
2. This GameObject has a mesh as it's child that uses a SkinnedMeshRenderer.
3. For some reason the Skinned Mesh Renderer is triggering the Physics.SyncTransforms() function. Sometimes up to 9 times per frame randomly.
4. When I have 5000 of this types of GameObjects the Physics system has a 12-13 ms cost even when I'm doing nothing with the GameObjects.
5. If I move the GameObjects with the SkinnedMeshRenderer removed, Physics.SyncTransforms() does get called, but it only costs 1ms.
6. Using a Mesh Renderer instead of a SkinnedMeshRenderer does not call Physics.SyncTransforms().
7. The SkinnedMeshRenderer does have an Animator in the parent, with "Animate Physics" set to false.
8. I've tried removing all components and only leaving the parent Collider and the SkinnedMeshRenderer, but the issue persists.
9. I've tried moving the collider to a second child so that the SkinnedMeshRenderer isn't a a child of a collider, still the same issue.
10. I've tried setting the Physics Simulation mode to Script and then only call it once per frame a "GameManager" Update void, still same performance issue.

Any help would gladly be appreciated.

Thanks for your time!

[obtuse umbra]

im trying to make water droplets, that roll around easily, not having much luck. any ideas?

[obtuse umbra]

and if theres not a physics solution is there a shaders solution, so like it looks like a softbody but its actuallly just spheres or smth

[obtuse umbra]

nvm got it

[river minnow]

does Physics2D.OverlapPoint() not work with Tilemaps?

I can't seem to get OverlapPoint or Raycast to detect Tilemap collision

[tiny flame]

How can i fix this? this is my throw code;

        if (Input.GetMouseButtonDown(0)) {
            rb.isKinematic = false;
            interactBase.haveParent = false;
            rb.AddForce(transform.forward * throwForce, ForceMode.Impulse);
            transform.SetParent(null);
            didThrow = Teacher.Instance.isTeacherAngry;
        }

[hollow wind]

1. Kinda hard to tell from the video and the code, but maybe the ball is overlapping another collider and it get depenetrated really fast. There is a float called Depenetration Speed that you can change in the Physics settings in Project Settings. Change that value and see if the result is different.
2. I love your project idea of throwing stuff in the classroom good job!

[woeful pulsar]

Is there a built in method to get a layermask from the collision matrix?

[bleak umbra]

No, you’d have to construct that yourself from individual checks.

[eager olive]

I seem to have accidentally broken the first law of thermodynamics with my physics setup

I'm trying to create this wheelchair controller in which you control only the big two wheels on the back

when I play it just rides off into the sunset

this is without applying any torque to the wheels. I find it odd that it's just accelerating out of nowhere.

[timid dove]

The fact is that PhysX is optimized for performance rather than physical accuracy. There's no guarantee that things like conservation of energy or momentum will be honored

[tiny flame]

Thanks a lot ❤️ I tried what you said, but it didn't work, I didn't dwell on it much because it was a jam game. Thanks anyway.

[flat canopy]

Btw What value should it be? Should we increase or decrease? In our case, the value appears to be 10.

[hollow wind]

Well if you want to make a collider depenetrate another more slowly you must lower the value, and if you want it faster you increase it

I think it’s in meters per second

So you have it set to 10m/s right now, which is quite fast by default

[clever path]

why does exiting and entering my unity project fix things? e.g. whenever my physics arent working properly i just leave and reenter and it gets fixed for some reason

[timid dove]

What is the nature of "physics aren't working properly"?

That shouldn't be happening at all. Maybe you have framerate dependent code in your project

[fossil tangle]

Just needed to say this: I hate (Unity's) Joints. 😂. Whoever invented the logic for .anchor and .axis (and made them invisible in editor, corruptible in runtime, and not directly settable) was a sadist

I think I've just discovered that you literally cannot create Joints except inside FixedUpdate - no matter what settings you give them, Unity runs physics first, moves them a little, then sets the private internal config that is "inferred" from your actual public config. ugh ugh ug

[timid dove]

At this point you might be the world's foremost expert in Unity's Joint system

[fossil tangle]

(which makes sense, but is so horribly non-Unity a wayy of doing things)

This also means: by definition you cannot debug unity physics joints in the editor - as soon as you hit Play, you only have "partial influence" over what happens (since editor does not submit updates during FixedUpdate). Literally broken across the board: physics + editor = fail. You have to write custom inspectors for every joint that do what Unity's inspectors were requried to do, but don't

(this also would explain a LOT of the problems I've seen 1st hand and 2nd hand over the years with 3rd party Unit physics assets, where they go ... really really wrong ... when debugging/editing a game)

All 4 wheels here are - by definition - upright at all times. Only they aren't. The rear ones... OK, the spring force is too weak, so they 'collapse' when having to push out too hard sideways against the ground. But the front ones ... I set the spring force higher in editor, at which point unity aribitrarily instantly changed the 0-angle for some of the joints. https://www.youtube.com/watch?v=DJ0Aq1B5xHU

[pseudo marlin]

Anyone here able to help out with some physics troubles I am having. I am fighting with colliders and trying to get a slider joint to work right and things are just not lol

Link is to my problem : #💻┃code-beginner message

[flint portal]

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[opaque relic]

Hi all,

I'd like some direction on how to achieve a Sims-like object hover highlighting. When the cursor hovers directly over an object, I'd like to enable an outline.

My first thought is to raycast from the cursor every frame and return any hit objects on the layer I'm interested in.

My issue is the collider shape. The screenshot attached shows a shelf with a mesh collider attached. The mesh is the same mesh used by the shelf, yet it isn't bound to the shelf in the way I'd expect.

So two questions,

1. Am I approaching the problem in the right way (raycasting to a collider)? Do games like The Sims work this way?
2. If so, how do I make my mesh more precisely outline the object?

Any help is much appreciated, thank you!

[timid dove]

• yes Raycasts are used for this
• no you don't need to write the logic for this yourself
• Make sure you have an Event System in your scene
• make sure you have a PhysicsRaycaster on the camera
• Attach an EventTrigger component to your object and add PointerEnter and PointerExit events to it
• Alternatively attach a script to it which implements IPointerEnterHandler and IPointerExitHandler

As for the collider shape if you want a "tight" shape you should uncheck the "convex" box on the MeshCollider. Note that if it's not convex it can't have a dynamic Rigidbody, which is probably not necessary for you anyway

Some more info: https://docs.unity3d.com/Packages/com.unity.ugui@2.0/manual/SupportedEvents.html

[opaque relic]

Brilliant, this community always delivers! I've used the Event System for UI interactions, but was doing my own raycasts for object hits. This approach makes a lot more sense, thanks!

[timid dove]

Yes and the beauty of using the same system as the UI system here is you will get things for free like UI blocking this behavior

[normal wren]

so, I have a situation where I have a self contained world attached to a gameobject. That gameobject is moved around by code. I want there to be some physics in that little world. However, it all explodes when it's being translated around by said code. Works fine when that's turned off. What would be the right approach to get around that?

can you look, set a world node transform from which everything is calculated

[timid dove]

Use multiscene physics

i.e. do the physics for the little world in another scene. Use proxy object children of the world for rendering

[normal wren]

thanks for the answer, sounds like kind of a pain, any faster options? 😄

(it's just one small instance so very hacky is fine)

[cerulean copper]

For a 3d game, with a character, should I use a rigid body or a character controller?

with the character controller the character is "kinda" floating around & the character won't rotate and move according to the terrain (since it's not flat)

I just started learning unity today btw so sorry if this is an abvious one 🙂

[ionic escarp]

I am getting a Vector3 from the transform to mouse position then I'm normalizing it and "shooting" an object in that direction, why does the velocity depend on the distance from shooter to the mouse? The further I get the faster the object moves, shouldn't it be the same since I'm normalizing the vector?

[timid dove]

For a 3d game, with a character, should I use a rigid body or a character controller?
Both have their uses. It really depends on the exact movement style and feel you want. I would recommend getting very familiar with both types and deciding which suits your game the most.

[timid dove]

Show your code. If you normalized it, the distance shouldn't matter. You probably have a bug in your code.

[ionic escarp]

private void Shoot()
{
    // Vector from spaceship to the mouse position
    Vector3 diff = Camera.main.ScreenToWorldPoint(Input.mousePosition) - transform.position;
    // Normalize to length 1.0
    diff.Normalize();

    // Z angle for bullet direction
    float rot_z = Mathf.Atan2(diff.y, diff.x) * Mathf.Rad2Deg;

    // Create bullet object, set position and rotation, and shoot with speed 15 * direction
    GameObject bullet = Instantiate(bulletPrefab);
    bullet.transform.SetPositionAndRotation(gunHead.transform.position, Quaternion.Euler(0F, 0F, rot_z + 270));
    bullet.GetComponent<Rigidbody2D>().velocity = (Vector2)diff * 15;

    Debug.Log("Shooting with direction vector: " + diff);
}```

[timid dove]

It's because you are normalizing the 3D vector

part of that is a Z distance

you are then ignoring the Z distance in your physics since you are using 2D physics

    Vector2 diff = Camera.main.ScreenToWorldPoint(Input.mousePosition) - transform.position;
    // Normalize to length 1.0
    diff.Normalize();```
try this

[ionic escarp]

Ah makes sense, thank you

[ionic escarp]

Yep that worked

[worldly dome]

I want to make a Rigidbody that is ONLY affected by gravity. ONLY. But Kinematics aren't affected by gravity. How can I accomplish this?

[fleet adder]

A layer that is set to not collide with anything, could work here

You can set the collision matrix in the physics settings

[worldly dome]

Sorry, I didn't specify: I still want the object to have collision. I pretty much want it to be a Kinematic Rigidbody that is affected by gravity.

oh wait i figured it out

[fleet adder]

So you want collision, you want gravity, but what do you not want? Do you want it simply not affected by the collisions? Do you want it to never roll after being affected by gravity (as in no sideways movement)? I'm confused

[worldly dome]

i can just add velocity

[worldly dome]

no all i want is an object that falls when there's nothing under it and that's it

i figured out that I can just make a rigidbody and add velocity downwards equal to the gravity

[fleet adder]

Acceleration, not velocity. But yeah that works

[worldly dome]

👍

[blazing narwhal]

Hello guys i have a question what is better to achive ground check on 2D OnCollisionEnter2D or OverlapCircle()?

[gleaming totem]

hi, why my character floats if I set the collision correctly?

I aplied rigidbody but the collision is bigger than the debugging

it's not my ground check logic because it's doesn't stop the gravity

[timid dove]

your objects are all really small

and Settings -> Physics2D -> Default Contact Offset is a thing

[gleaming totem]

thanks

[fossil tangle]

Anyone here used "hasModifiableContacts" and "public void ModificationEvent(PhysicsScene scene, NativeArray<ModifiableContactPair> pairs)"?

It was working perfectly, but then ... it seems to be broken for 'break forces'

i.e. I don't receive any ModificationEvent, but two colliders that overlap get a large force on them... if they don't overlap: no force. But if they overlap: force + no ModEvent. ... whaaa??

...
i.e. this:

joint.currentForce

... appears to be calculated without ever looking at the contacts, and so any attempt to modify the contacts ... has no effect on it 😦

[timid dove]

I've never used it in the context of joints, only to modify collisions. I see you're getting into the deep corners now 😉

[fossil tangle]

It is ... so close ... to now working (although I've had to accept a lot of trashy behaviour by Unity physics along the way)

Hmm. Actually when I have e.g. "15 child colliders making a compound collider" ... and that object is resting on the floor ... Unity sends 15 copies of ModificationEvent, but ALL OF THEM are between the 'first collider' and 'the floor' ...

That cannot be correct - I think that might be half the problem

I think it's a bug in Unity2022LTS - the modificationevent API just ... fails. The more I think about this: the project used to do what you'd expect (for N colliders, you'd get NxN events, with unqiue pair on each event) ... and it doesn't any more. I haven't changed the code (checked in git), and I've restarted Unity a few times, but somehow the physics subsystem has got broke 😦

[fossil tangle]

Restarted again - suddenly started working. Unity2022LTS is ... not great.

[vocal jewel]

Good morning. Is it possible to minic animations using physics? For instance, if you have a humanoid, could you force the hands to be stuck to a object, and then make it jump?

[hollow basin]

How do I add a collider that firs this bridge mesh? I currently have mesh collider component and mesh filter component addded, but the player can still walk throught the bridge. How do I fix this?

[open tusk]

yo guys, which physics should i use for a player that he doesnt get dragged down if hes on a hill

[timid dove]

You'd do that with inverse kinematics

[timid dove]

Are you using 2D physics or 3D?

[timid dove]

Friction or manually add a counteracting force to prevent this when on slope

[runic torrent]

I'm not sure I'm going to be asking this correctly, but how would I go about calculating what the gravity decay has to be so that an object will jump up 2m over 1 second given a velocity of (0,1,0) before falling back down?

[open tusk]

Friction joint 2d?

[timid dove]

no just friction

using physics materials if needed

[open tusk]

isnt there

[timid dove]

friction is there. It's always there. It depends on physics materials (and there's a default one on everything if not assigned)

[open tusk]

cant screenshot how its not there

[timid dove]

I didn't ask for one

[open tusk]

add component

then search

not there

[timid dove]

it's not a component

https://docs.unity3d.com/Manual/class-PhysicsMaterial2D.html

[open tusk]

doesnt work

my player still slides down the hill

and glitches out the map

[timid dove]

It works fine, but it will depend on the details of the situation and your code

also I did suggest an alternative as well

[open tusk]

so i have to code a second gravity that pulls up the character?

that doesnt maek any sense

[timid dove]

not up just a counter force to the sideways force created by the slope

that's how real life works

in real life when you stand on a slope, you are pushed sideways, but you use friction to counteract it and stay still

physics in the game engine works the same way

[open tusk]

how do i use this friction?

i set friction to 50 and bouncy to 0

[timid dove]

The link I sent explains how to use it

[open tusk]

not realy

just the functions of it

but it doesnt do anything

[timid dove]

If you read the whole page it explains how to use it