Find the "tension" on a rope constraint

[tranquil cairn]

I'm trying to simulate "tension" on a RopeConstraint. The attachment also has a LinearVelocity constraint acting on it. How would I find the tension?

[vapid sentinel]

T = m * a

[potent coral]

simulate or find tension

[tranquil cairn]

Does this seem accurate? @potent coral

[delicate turtle]

well tension how

is it like a part stuck to a wall

i mean the string

[tranquil cairn]

its a part floating in water, with another LinearVelocity acting on the same attachment as the RopeConstraint

(a "fish")

[delicate turtle]

i dont understand the situation

break it down like its a physics problem at school

[tranquil cairn]

where Fw is the force from the winch of the RopeConstraint

and Ff is the force from the LinearVelocity or "fish"

theta is the angle of the RopeConstraint

pretty sure theta would be:

local diffY = Pointer.Position.Y - Device.Position.Y
local diffXZ = (Vector2.new(Pointer.Position.X, Pointer.Position.Z) - Vector2.new(Device.Position.X, Device.Position.Z)).Magnitude
local angle = math.abs(math.atan2(diffY, diffXZ)) --angle between two points: atan2(yb - ya, xb - xa)

Pointer is the bobber (in the water), the part with both forces acting on it

and Device is the end of the rod (near the character)

[fathom blade]

@tranquil cairn more specific use case pl0x

oh i didnt see

its for feesh

[tranquil cairn]

feesh indeed

[delicate turtle]

theta doesnt even matter

[tranquil cairn]

it do

[delicate turtle]

since its relative to the tension

[delicate turtle]

look at how u drew the arrows

its parallel to the tension

just get the sum of force parallel

[tranquil cairn]

yeah but that's something I have to derive myself

[fathom blade]

get rope length, get rope stretchy amount before no more stretch, that is ur window, then calculate percent

ezpz

[delicate turtle]

its not deep

[tranquil cairn]

rope length doesnt replicate

[fathom blade]

it shouldnt have to

it doesnt need to change

also you can manually replicate no?

[tranquil cairn]

it is changing

[tranquil cairn]

i did

[fathom blade]

then calculate it again

[delicate turtle]

T +Fw - F_F

[fathom blade]

why is it changing

[tranquil cairn]

reel feesh

[fathom blade]

its a window

window move

its ok

just keep calc window

ezpz

[tranquil cairn]

i have to deliver this POC today, im stressing

[fathom blade]

blud is not listening

[delicate turtle]

POC?

[fathom blade]

you dont appreciate the window

person of color

he sells slaves

[delicate turtle]

bruh

[oblique egret]

just wondering

[fathom blade]

proof of concept

[oblique egret]

why do you need to know the tension force

is it for a meter of some kind

[fathom blade]

2 businessy words for you haze

[tranquil cairn]

yes exactly

[fathom blade]

proof of concept POC

and minimum viable product MVP

[delicate turtle]

ok lol

[elfin anvil]

yo

thought we were talking about tension

whats going on

[fathom blade]

i feel tension now that youre here

[delicate turtle]

^

im telling him theta doesnt even matter

[fathom blade]

@tranquil cairn is the tension an indicator for line break or does it have other effect

[delicate turtle]

well it does bc u did it relative

nvm

[tranquil cairn]

the X and Z angle of F_f can also change

[fathom blade]

you guys are overcomplicated ts wtf

[tranquil cairn]

yeah pretty much

[delicate turtle]

oh what the hell

its 3d?

[tranquil cairn]

2D

[delicate turtle]

oh 2d

[fathom blade]

bro

[oblique egret]

what

[fathom blade]

just measure the difference and choose a window

distance

ill draw

1 has slack, no tension

2 is taught, but no stretch, min tension

3 is streched to max, max tension

you set a window on 2 and 3

and measure a percent to calculate a tension value

then its all application code

does that make sense

[tranquil cairn]

that was the original idea, but I haven't been able to pin down that length there's too much noise

[fathom blade]

what do you mean pin it down

you set it

[tranquil cairn]

the first of which is the replication of the RopeConstraint.Length

I;m using an unrelaible to replicate is

[fathom blade]

doesnt the client handle that anyways?

[tranquil cairn]

so noise from latency

[fathom blade]

you just need to keep track of sim on server and do sanity checks

[tranquil cairn]

no, I need to handle it on the server

[fathom blade]

but I mean why are you replicating

[tranquil cairn]

because of how these goons have this set up

[tranquil cairn]

because I wont be able to compare the length (which changes from using the winch) otherwise

[fathom blade]

then only replicate when they use the winch and match the sim

why dont you just do it all on the server

[errant ginkgo]

ugh physics

[fathom blade]

client can be visual mostly

[tranquil cairn]

I am, but the actual RopeConstraint is in a tool which is in the player's backpack

so the actual sim is on the client for the winch

[fathom blade]

wadafuck

[tranquil cairn]

even if it's enabled on the server

[fathom blade]

so change it

lmao

[tranquil cairn]

it's too late for that

[fathom blade]

so what you are having the client tell the server how the rope is doing?

wtf

why is it too late

[tranquil cairn]

yes lmao

[oblique egret]

that feels unsafe

[fathom blade]

its not too late

[tranquil cairn]

I gave them an estimate for today

[fathom blade]

its an easy switch tho'

[tranquil cairn]

and they dont know how this shit works

[fathom blade]

on equip just spawn it

on unequip despawn it

then you can have server sim

cant be that gnarly to do

and it solves ur problems

right

[tranquil cairn]

I just know it's going to break a bunch of other shit

[fathom blade]

what else does the winch interact with

[tranquil cairn]

that wouldnt only be moving the winch

[fathom blade]

is the player immobile during fishing?

[tranquil cairn]

while casting the line yes

[fathom blade]

while its in the water too?

or just cast

[tranquil cairn]

just cast

[fathom blade]

that makes things harder

[tranquil cairn]

look at this shit

[fathom blade]

blud is solving the 3 body problem for fish to get robux simulator

[fathom blade]

so, the physics are still replicated yeah

[tranquil cairn]

not the constraints themselves

[fathom blade]

so you can calculate tension based on velocity changes due to the ropes bonce propery

[fathom blade]

but the effects are

[tranquil cairn]

only how they interact with parts

[fathom blade]

yes

[tranquil cairn]

I have 0 restitution rn

[fathom blade]

so serverside you can keep a constant of the ropes properties that dont change

that shouldnt change

then use those and the velocity changes of the fish

to calculate tension

[tranquil cairn]

everything about the rope changes except for the pretty much

[fathom blade]

but you have to factor fish behavior

how does the fish work

does it swim arond

[tranquil cairn]

yeah, wait a certain amount of time, apply a LinearVelocity in an 2D direction XZ

[fathom blade]

serverside or client

[tranquil cairn]

wait more, then again

server

[fathom blade]

good

so any changes that deviate you can attribute to rope

then you can make your own virtual tension that feels good for the game

does that make sense

the math doesnt matter, just get a delta and balance

[tranquil cairn]

that was the idea here:

[fathom blade]

didnt work?

[tranquil cairn]

yeah it makes sense, but the math matters a little, because of possible edge cases

and the actual math is a bit over my head

[fathom blade]

the math doesnt matter at all

edge cases like the fish hitting the lake border should just be squished

[tranquil cairn]

as long as it comes out to a linear function yeah

[fathom blade]

in fish behavior

[tranquil cairn]

I just dont want to end up with a concave function

[fathom blade]

you could also not base it on force at all

[tranquil cairn]

I was thinking time

[fathom blade]

you could base it on angle change from original path

[tranquil cairn]

that would be pretty easy

[fathom blade]

time?

just a timer

cringe!

[tranquil cairn]

yeah that would suck

[fathom blade]

angle change is decent I think

cause if the fish is going towards you

less tension

away more

and it balances naturally

[tranquil cairn]

hmm that could work

but my brain is fried

[fathom blade]

imagine a circle

also

does ur fish have a Y axis

[tranquil cairn]

no

[fathom blade]

good

[tranquil cairn]

it doesnt pull on the Y

[fathom blade]

yeah just calculate an angle

and then subtract

however many degrees different it is apply tension

then playtest it and see what feels good

thats good enough for POC

you can make it better later

[tranquil cairn]

different from what though

[fathom blade]

different from the fish's movement

so, when the fish is moving, then you check tension

when it isnt, you can default to no tension

[tranquil cairn]

yeah I'm only checking when it's pulling

[fathom blade]

when its pulling?

the fish/

?

[tranquil cairn]

moving

yeah

[fathom blade]

ah

yeah otherwise apply 0 tension

[elfin anvil]

ok

im back

do we still need help

[fathom blade]

@tranquil cairn

1 is max tension

2 is 0.5x tension

thats linear

you may want to alter the formula, but thats the basics

arrow is fish movement direction

[elfin anvil]

what the

[tranquil cairn]

I'm just trying to figure out a formula for it

[elfin anvil]

i gotchu jcx

[fathom blade]

just make anything

and playtest it

[elfin anvil]

theres a vid i rmbrw

i watched

[fathom blade]

then you will know how to make formula

[elfin anvil]

5 minutes

gives u formula

and snapping point

[tranquil cairn]

bet

will try in the meantime

thanks bluds

[fathom blade]

linear might be good enough

yw

[elfin anvil]

https://www.youtube.com/watch?v=qfYNjEWs2u8

[tranquil cairn]

that's just to stop the fish from moving

[fathom blade]

wow looks like @elfin anvil fucking sucks and you should do my idea

[elfin anvil]

bro u can infer ok

mb

[delicate turtle]

i am taking ap physics c mechanics

like if you want

format this into a whole frq question

ill derive everything for you

I tink

[tranquil cairn]

I formatted everything except for the change in angle for F_f

[delicate turtle]

also do u still need help?

ask chat gpt for this

dont ask it to code it

ask it to derive the equation

and ill fact check it

im too lazy to frikin do it rn

[tranquil cairn]

not sure, testing out a solution rn

[delicate turtle]

ok

[tranquil cairn]

fact check the one i did?

[delicate turtle]

well idk ur steps on how u derived it

its just a bunch of code

can i see ur work on paper

[tranquil cairn]

didnt do any

[delicate turtle]

nvm im js wasitng ur time 💀

then we r cooked

[tranquil cairn]

@delicate turtle @fathom blade @elfin anvil

[elfin anvil]

😭

[fathom blade]

HELL YEAH'

[delicate turtle]

W