get_aabb() returns AABBs with incorrect position-values

[okapii]

Godot version:
Godot v3.2.3.rc6.official

OS/device including version:
MacBook Pro (13", 2020)
2,3 GHz Quad-Core Intel Core i7
16 GB 3733 MHz LPDDR4X
Intel Iris Plus Graphics 1536 MB

Issue description:
I hope that this is not a conceptual misunderstanding on my end but it seems to me that the position property of AABBs is reporting incorrect values.

extends Spatial

func _ready():
	print($box1.get_aabb())
	print($box2.get_aabb())
	print($box2.get_aabb())

Running this code on the scene shown above yields the following output:

• -0.5, -0.5, -0.5 - 1, 1, 1
• -0.5, -0.5, -0.5 - 1, 1, 1
• -0.5, -0.5, -0.5 - 1, 1, 1

As one can see all position values are identical despite the cubes being positioned differently.

Originally I assumed that this was by design and that one would have to offset the AABBs utilising the object's origin-coordinate to get the correct position of the AABB in the global world. But that surely can't be right as this would result in varying / wrong values depending on where the origin is positioned in relation to the actual geometry.

Steps to reproduce:
See above

Minimal reproduction project:
200915_Godot_AABB.zip

[Calinou]

@okapii Did you find a solution to this issue?

[okapii]

@Calinou : I thought I did. But by now I am even more stumped. :) Right now I am just unsure if this is a bug or an issue on my end which is why I did not reopen things.

I have come to realise that the AABBs never reflect position, rotation and scale of instances. get_aabb() always leads to the bounding box of the unrotated, unscaled object positioned at the origin resulting in false collision detection. Position can be accounted for by altering the AABBs position-property according to the instance's origin but I am fairly stumped now as to how to account for rotation and scale. Sadly I can't find too much information on the whole AABB topic in Godot in general.

[okapii]

As I still can't seem to find a solution here is an illustration of the issue. It is still the basic code form above.

Scene in perspective

Intersection false

Intersection true

extends Spatial

func _ready():
	var b1 = $box1.get_aabb()
	var b2 = $box2.get_aabb()

	b1.position += $box1.translation
	b2.position += $box2.translation

	print(b1.intersects(b2))

As one can see what matters is not the actual position / rotation / scale (as seen on the left side of the images) but the default rotation where in the 2nd one this leads to a small intersection while in reality both versions should report "true" as the bounding boxes should intersect.

[pouleyKetchoupp]

Could you check if get_transformed_aabb gives you the right result? It looks like get_aabb is the bounding box in local space, while get_transformed_aabb is in world space.

[okapii]

Yeh, that was the obvious solution I was afraid of potentially just not seeing. So yeah, thanks, that worked!

I guess the method is not documented in https://docs.godotengine.org/de/stable/classes/class_aabb.html for being inherited from VisualInstance?