Setting transform of meshes in MultiMesh produces an error

[Zylann]

Godot 3.0 alpha 2, Windows 10 64 bits
nVidia GeForce 940M

As an attempt to answer @abhaskumarsinha, I found out this code doesn't work:

extends MultiMeshInstance

func _ready():
	# Create multimesh resource that will contain 4 cubes
	var mm = MultiMesh.new()
	mm.instance_count = 4
	mm.transform_format = MultiMesh.TRANSFORM_3D
	mm.mesh = preload("res://cube.obj")
	
	# Set position of all cubes at random
	for i in range(mm.instance_count):
		var pos = Vector3(rand_range(-2, 2), rand_range(-2, 2), rand_range(-2, 2))
		var t = Transform(Basis(), pos)
		mm.set_instance_transform(i, t)
	
	# Assign multimesh to be rendered by the MultiMeshInstance
	self.multimesh = mm

It shows only one cube, and 4 errors are logged, everytime instance transforms are set:

ERROR: RasterizerStorageGLES3::multimesh_instance_set_transform: Condition ' multimesh->transform_format == VisualServer::MULTIMESH_TRANSFORM_2D ' is true.
   At: drivers\gles3\rasterizer_storage_gles3.cpp:3825

But as shown in the code, I did set the format to 3D...

Edit:
It works if I assign transform_format before setting instance_count. I didn't expect these to be order dependent.

[djrm]

it is clear why you need to call transform_format and color_format, before setting the instance count, (it allocates and configures everything when you do that) but the name of the method is not very descriptive, another option would be to configure again when setting the formats.

[Zylann]

At first I thought it was a bad idea to expose this as a property, but that makes sense when you know how it's implemented. I wonder which kind of magic Godot does to keep these ordered as properties.

[reduz]

This is not really a bug, but an error should be shown if format or something is changed before instance count. Is an error being shown or should we add it?

[Zylann]

@reduz only this, in the console as usual:

ERROR: RasterizerStorageGLES3::multimesh_instance_set_transform: Condition ' multimesh->transform_format == VisualServer::MULTIMESH_TRANSFORM_2D ' is true.
   At: drivers\gles3\rasterizer_storage_gles3.cpp:3825

[akien-mga]

We have now entered release freeze for Godot 3.0 and want to focus only on release critical issues for that milestone. Therefore, we're moving this issue to the 3.1 milestone, though a fix may be made available for a 3.0.x maintenance release after it has been tested in the master branch during 3.1 development. If you consider that this issue is critical enough to warrant blocking the 3.0 release until fixed, please comment so that we can assess it more in-depth.