CSGMesh GetAabb() / GetTransformedAabb() returns zero

[chhjel]

Godot version:
3.2.2.beta1

OS/device including version:
Windows 10 Pro (10.0.18362)

Issue description:
CSGMesh methods GetAabb() and GetTransformedAabb() returns Vector3.Zero.
csgMesh.Mesh.GetAabb() seems to return the correct value.

Steps to reproduce:

1. Create a CSGMesh node.
2. Add any mesh to it.
3. Call GetAabb() or GetTransformedAabb() on the CSGMesh node.
4. Zero-value is returned from the methods.

[madmiraal]

This happens with all CSG shapes, not just the CSGMesh.

Update: This appears to be a timing issue, because it only happens when calling the functions in _ready(). When calling them in the _process() loop, for example, they have been calculated and are available.

[mrushyendra]

To calculate the AABB for a CSG Shape, it looks like _update_shape() needs to be called, which will in turn create the CSGBrush and calculate the bounding box.

godot/modules/csg/csg_shape.cpp

Lines 200 to 212 in d3c10e8

	if (n) {
	AABB aabb;
	for (int i = 0; i < n->faces.size(); i++) {
	for (int j = 0; j < 3; j++) {
	if (i == 0 && j == 0) {
	aabb.position = n->faces[i].vertices[j];
	} else {
	aabb.expand_to(n->faces[i].vertices[j]);
	}
	}
	}
	node_aabb = aabb;
	} else {

Currently, it seems like _update_shape() is not called in the CSG shape's constructor, which is why calling get_aabb() in _ready() returns a zero vector. I tried adding a call to update_shape() from the constructor, but this alone does not seem sufficient. This is because properties like the width, height, etc. are only updated afterwards, which means that the AABB calculated in _ready() is the default, and not the latest one updated with values from the editor.

[hoontee]

CSGShapes update in a deferred call in order to prevent each individual child shape from updating upon entering the scene tree.
Since this is intentional, the only solution is to use call_deferred:

func _ready():
	call_deferred("deferred")

func deferred():
	print(csg_shape.get_aabb())