Path (3D) seems to make a wrong rotation

[rogeriodec]

Godot version:
3.1

OS/device including version:
Windows 10 x64

Issue description:
I did a Path / Pathfollow (by GdScript) with a form more or less equal to this (a capsule):

The coordinates in the code are:

	var p = $Path.curve
	# right curve
	p.add_point(Vector3(0, 0.35, 0), Vector3(0, 0, 0), Vector3(0, 0, 0))
	p.add_point(Vector3(0.35, 0, 0), Vector3(0, 0.35, 0), Vector3(0, -0.35, 0))
	p.add_point(Vector3(0, -0.35, 0), Vector3(0, 0, 0), Vector3(0, 0, 0))
	
	# left curve
	p.add_point(Vector3(-dist_eixos, -0.35, 0), Vector3(0, 0, 0), Vector3(0, 0, 0))
	p.add_point(Vector3(-dist_eixos - 0.35, 0, 0), Vector3(0, -0.35, 0), Vector3(0, 0.35, 0))
	p.add_point(Vector3(-dist_eixos, 0.35, 0), Vector3(0, 0, 0), Vector3(0, 0, 0))
	
	#close path
	p.add_point(Vector3(0, 0.35, 0), Vector3(0, 0, 0), Vector3(0, 0, 0))

I did a mesh like a tile to follow the Path. 0 rotation.
However, the mesh is following the Path with a sligth rotation.

Steps to reproduce:

Run the Scene on the attached project

Minimal reproduction project:
path.zip

[wombatstampede]

I jumped on a similar issue and did my own code to follow the path. It is slightly different, as I limited the following and rotation to X/Z (so rotating around Y) and the object positions between two points according to its length. You also get any errors free. But perhaps it helps someone out until the fix is done and in a release.:

tool
extends Spatial

export(float,0.0,1.0,0.001) var offset_relative = 0.0 setget set_offset_relative
export(float) var object_length = 15.0

func _ready():
	doUpdate(offset_relative)

func set_offset_relative(newval):
	offset_relative=newval
	doUpdate(newval)

func doUpdate(newval):
	var p = get_parent()
	set_physics_process(false)
	if p is Path:
		var plen=p.curve.get_baked_length()
		var absOffs=fmod(plen*newval,plen)
		var offs1=max(absOffs-(object_length/2.0),0)
		var offs2=min(absOffs+(object_length/2.0),plen)
		var p1=p.curve.interpolate_baked(offs1)
		var p2=p.curve.interpolate_baked(offs2)
		var newpos=p1+((p2-p1)/2.0)
		transform.origin=Vector3(newpos.x,transform.origin.y,newpos.z)
		global_transform=global_transform.looking_at(p.global_transform.xform(Vector3(p2.x,transform.origin.y,p2.z)),Vector3(0,1,0))

[marcosn41]

Thanks for this code wombatstampede! Save my project! This bug stopped me for weeks. I only changed to affect Y too bacause this problem for me only appear when i change Y coord.

[KoBeWi]

Still valid in 8718107
Although this might be an issue with the path.

[QbieShay]

Still valid on 20/3/2021

simplescreenrecorder-2021-03-20_14.09.03.mp4

[fossegutten]

Still valid in 4.0 alpha 1.
Also in my project it seems on a looped Curve3D the rotations get more and more wrong for each lap the PathFollow3D does.