Placing and rotating MultiMesh instances along a curve

Glebastik

Hi there! Trying to generate a railroad along a Path. There wasn't any problems with rails (CSGPolygon rules). For placing sleepers I decided to use MultiMesh. I even managed to place instances along a curve, but I'm stuck with its rotation. I always had problems with transforms, so I can’t come up with anything useful.

That is a part of my code (var sleepers_distance declared in other place and is float):

var curve_length = curve.get_baked_length()
var sleepers_count = floor(curve_length / sleepers_distance)

$Sleepers.multimesh.instance_count = sleepers_count

for i in range (0, sleepers_count):
	var t = Transform()
	var f = i * sleepers_distance
	t = t.translated(Vector3(curve.interpolate_baked(f)))
	$Sleepers.multimesh.set_instance_transform(i, t)

Here is the result.

MeshInstance "Sleepers" is a child of Path, script is attached to Path also. How can I rotate instances according to curve?

dave-the-dev

Try this...

func align_sleepers():
	var curve_length = curve.get_baked_length()
	var sleepers_count = floor(curve_length / sleepers_distance)
	$Sleepers.multimesh.instance_count = sleepers_count
	for i in range (sleepers_count):
		var t = Transform()
		var f = i * sleepers_distance
		var f_plusone = (i + 1) * sleepers_distance
		var sleeper_position = curve.interpolate_baked(f)
		var next_sleeper_position = curve.interpolate_baked(f_plusone)
		var facing_direction = (next_sleeper_position - sleeper_position).normalized()
		var up_vector = curve.interpolate_baked_up_vector(f)
		t = t.translated(sleeper_position)
		
		t.basis.z = facing_direction
		t.basis.x = t.basis.z.cross(up_vector).normalized()
		t.basis.z = t.basis.y.cross(t.basis.x).normalized() * -1
		
		$Sleepers.multimesh.set_instance_transform(i, t)

Post a picture if it works, I'm curious to see how it looks in your project. ^_

Glebastik

@"Dave The Dev" It works perfect except for the sleepers turned inside out :#

dave-the-dev

HA! Its a good thing I'm not in charge of doing the math for anything important... like teleporters.

Multiply this line... t.basis.z = t.basis.y.cross(t.basis.x).normalized() by -1, like this... t.basis.z = t.basis.y.cross(t.basis.x).normalized() * -1

and let me know how is goes... :lol: I also edited the code above, so if it works, that post can be your answer.

Glebastik

Awesome! Thank you!

Glebastik

Everything was fine until I started making slopes. Sleepers are arranged horizontally although they should follow the gradient. I didn't dare to poke around the code and decided to ask advanced people again :)

Some elements of vector math are still like a dense forest for me...

P.S. It would be nice to take tilting into account for resolving probable issue in future.