Help with ShapeCast3D Collision and Sliding

[Bob]

Godot Version

4.4

Question

Hi! I recently decided to make my own Character Controller from scratch and I came to a problem of collisions. I used this tutorial and came back with this function:

func collideAndSlide(distanceToTravel : Vector3, depth : int):
	if (depth >= MAX_BOUNCES):
		return Vector3.ZERO
	
	var distance : float = distanceToTravel.length() + SKIN_THICKNESS
	
	collider.target_position = distanceToTravel.normalized() * distance
	collider.force_shapecast_update()
	if collider.is_colliding():
		var hitDistance : float = distance * collider.get_closest_collision_safe_fraction()
		var surfaceSnap : Vector3 = distanceToTravel.normalized() * (hitDistance - SKIN_THICKNESS)
		
		var leftoverTravel : Vector3 = distanceToTravel - surfaceSnap
		
		if surfaceSnap.length() <= SKIN_THICKNESS:
			surfaceSnap = Vector3.ZERO
		
		for i in range(collider.get_collision_count()):
			var normalPlane : Plane = Plane(collider.get_collision_normal(i))
			leftoverTravel = normalPlane.project(leftoverTravel)
			velocity = normalPlane.project(velocity)
		
		print(leftoverTravel)
		
		return surfaceSnap + collideAndSlide(leftoverTravel,depth+1)
	
	return distanceToTravel

And while this does work, it has several small bugs surrounding it that I am unsure of how to solve. In this video example you can see how it jitters when it sliding into a corner, how the physics are seemingly random and slow-down when moving against the wall and the margin often bugs and you can see how the collider is a certain distance away before sliding, but then suddenly when you go at an angle into a wall it snaps you closer.

[Bob]

So, what I learnt is that ShapeCast’s aren’t accurate which is why the margin error was happening so I’m looking into new ways of implementing this.