Not sure if I knew the exact term but

[nocturne hornet]

I make a thread as to not monopolize the conversation

[earnest flume]

Fair enough

[nocturne hornet]

so the thing is when your character move, there is two way to express his movement

either you look at its coordinates in Unity, and describe their changes

this is what we call a global frame of reference

it's global because everyone has the same origin

the same (0, 0)

but you could also describe it according to the player. If the player move 1 unit in front of them this vector would be described as (0, 0, 1) in their local frame of reference

[earnest flume]

        _oldPosition = transform.position;```

Would this be local frame of reference?

[nocturne hornet]

no, this is global. transform.position is always global

[earnest flume]

But using localPosition will give the same result if it's no childed, right?
Or am I thinking wrong

[nocturne hornet]

localposition gives you the frame of reference of the parent

[earnest flume]

Ahh

[nocturne hornet]

if there are no parent then yes it is global

[earnest flume]

Then I get that, just this is not clicking yet

Sorry, been working for most of the day already, so not as sharp as in the morning 😅

[nocturne hornet]

yeah linear algebra took me some time too dw :)

but see it this way. Imagine both your player and enemy move forward. They would have very different vectors in the global frame, but in their respective frame of reference, they both move along (0, 0, 1), right ?

[earnest flume]

Ah, yeah

[nocturne hornet]

ok, so what you need to do is take the local movement of the player, give it as is to the enemy, flip it, then have your enemy perform this movement as if it was in his local frame of reference

does it makes sense to you ?

[earnest flume]

I think so yeah

MovementPerFrame = transform.InverseTransformVector(transform.position - _oldPosition);
_oldPosition = transform.position;

This seems to give the right value for the player movement

[nocturne hornet]

Yes, it would give you the player's movement in the local frame of the player

[earnest flume]

_trackers.position += transform.TransformVector(_playerInfo.MovementPerFrame);

This mirrored correctly, so now I just gotta flip x

[nocturne hornet]

either x or z

I think it's z

anyway, gotta go now, good luck

[earnest flume]

Sure, thanks a bunch!
Think I'll get it working now!

[nocturne hornet]

👍

[earnest flume]

And learned some more linear algebra for games haha

[nocturne hornet]

linear algebra is the single most useful theory of maths when it comes to game dev

[earnest flume]

Ah shoot this almost worked

(dont feel pressured to respond btw)

Now when the player rotates so the forward is to the left of the enemy and moves forward the enemy moves to his forward instead of mirroring the player

The straight lines are the path I think. The dotted line is the desired path

The code rn would have worked if the player also would be forced to look at the enemy I think

[earnest flume]

Trying something to take into account the angle ```cs
var movementPos = transform.TransformVector(_playerInfo.MovementPerFrame);

        var newAngle = Vector3.Angle(-_trackers.forward, _player.transform.forward);

        var newVector = Quaternion.AngleAxis(newAngle, _trackers.up) * movementPos;

        _trackers.position += newVector;```

Bit better I think but not fully

[wooden ferry]

Use syntax highlighting

var movementPos = transform.TransformVector(_playerInfo.MovementPerFrame);

            var newAngle = Vector3.Angle(-_trackers.forward, _player.transform.forward);

            var newVector = Quaternion.AngleAxis(newAngle, _trackers.up) * movementPos;

            _trackers.position += newVector;

[earnest flume]

Got it

[wooden ferry]

Can't help with your issue though, not good with math, but I just wanted to say that you should apply syntax highlighting :P
(It helps for people who can help with the problem, readability is better :) )

[next scarab]

What exacyly are you trying to do?

[earnest flume]

Have an enemy behave like you are looking in a mirror basically

[next scarab]

There is many ways of “Mirroring”. So you want axial symmetric movement?

[earnest flume]

Yes

[next scarab]

And what would be the axis?

[earnest flume]

But there is no 1 axis, since the player can freely move. The enemy will procedurally spawn

[next scarab]

So you want your movement vector symmetric, not position.

[earnest flume]

What do you mean with that?

Sorry had math in dutch all my life so the terms are sometimes a bit fuzzy

[next scarab]

I will come back and explain soon

[earnest flume]

Sure!

[next scarab]

Okay is this what you want?

Where the blue is player and red is enemy

[earnest flume]

I think all enemys should have a 'mirror' between them and the player.
So if you look at the enemy at the bottom right and walk towards it, it will also walk towards you

If that makes sense

[nocturne hornet]

re

[nocturne hornet]

you can rewrite what is considered forward with a quaternion

so then if the player walks toward the enemy, it is counted as "forward"

[earnest flume]

So if you'd face an enemy and will walk into the enemy if you try to pass him

Fair enough, maybe I can figure out something like that next week

[nocturne hornet]

actually this mirror idea is not bad

you can simulate a "mirror" by reflecting the position either around an axis or a point

[earnest flume]

https://forum.unity.com/threads/calculate-mirror-position-over-tilted-axis.1218840/

Not sure how useful this would be, but might help

[nocturne hornet]

ok, so how to reflect a position around an axis

[next scarab]

Okay, so is this what you want?

[earnest flume]

The top right will go towards the player arrow

Then yes

[next scarab]

Oh yeah

[earnest flume]

Then you'll cross the enemy at all times if you try to get past

[nocturne hornet]

Ok, let me explain how to get that

[nocturne hornet]

to define a mirror, you need a point and an axis

the point will act as the origin for the frame of reference for the mirror

it is important than for all computations you do you use this point as the origin (0, 0, 0)

then, you take the position p you want to reflect

and you project it unto the mirror (using Vector3.ProjectOnPlane)

let's call p' the projected p unto the mirror

and r the reflection

then you get r = p' - 2p

hm wait

no wait that's for reflecting around a point

no wait again, the correct formula is 2p' - p my bad 💀

like that

So

For each of your enemies, give them a mirror. In Unity a plane is defined as a point and it's normal, (to get the normal, just take your axis and use Vector3.Cross(axis, Vector3.up)

[next scarab]

Okay, to simplyfy you can use Vector3.Reflect, where the direction is player’s movement vector, and normal is enemy to player direction. The result would be enemy’s movement vector

[nocturne hornet]

then for each frame,

Vector3 playerPos = player.transform.position - PlaneOrigin
Vector3 projectedPos = Vector3.ProjectOnPlane(playerPos, PlaneNormal)
enemy.transform.position = projectedPos * 2 + playerPos + PlaneOrigin

[nocturne hornet]

ooooh I didn't know Unity had a reflect function, that's cool

With reflect it'd look like this

void Update()
{
  Vector3 playerPos = player.transform.position - PlaneOrigin
  enemy.transform.position = Vector3.Refelct(playerPos, PlaneNormal) + PlaneOrigin
}

With PlaneOrigin and PlaneNormal the two variables you set to define your mirror

[earnest flume]

Alright, thanks a lot! Really appreciate it!
I will get into implementing this on monday and will update this thread when I do

[nocturne hornet]

ok ok ^^ ping me because by then I'll have forgotten

[earnest flume]

Sure haha