2D normal vector of a plane (collision.normal) isn't of magnitude 1 and isn't perpendicular to the plane

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:bust_in_silhouette: Asked By Shep


I have an issue with the normal from collision.normal

Given this piece code :

extends KinematicBody2D

var velocity : Vector2 = Vector2()
var move_speed : int = 60

func _ready():
	velocity = Vector2(3, 6) * move_speed

func _physics_process(delta):
	var collision = move_and_collide(velocity * delta)
	if collision:
		var n = collision.normal
		velocity = velocity.bounce(n)

CollisionShape2D for the ball (circle shape)

Sometimes, after a collision the normal n isn’t perpendicular to the plane and he doesn’t have a magnitude of 1, wich is not OK for a normal

There is a screenshot just after a collision with the wall to the right (this wall is perpendicular to the x axis).

As you can see :

n.x = -1
n.y = 0.000008
n magnitude ≈ 1.000000000032

Not perpendicular to the right wall, since the right wall is perpendicular to the x axis. normal should be = <-1, 0>
Because of that the velocity isn’t the same after a bounce, sure I can round n up or down.

Sometimes the normal is ok, sometimes not. Why is that ?

:bust_in_silhouette: Reply From: lofi

my guess is that the physics implementation have bugs, i was trying something similar relying in have the same value every bounce and it just simply never happened.