Odd issue with Animatable Body and child nodes

[phazorknight]

Godot Version v4.2.1.stable

Question

I’ve encountered an unexpected behavior with an AnimatableBody and certain child nodes.
It’s a bit hard to explain but I’ll try my best:

I have a custom class that controls a moving Platform, based on an AnimatableBody3D.

This platform can be controlled by a button (GenericButton), also a custom class that is a child of the platform (see image). This one in this case is also derived from an AnimatableBody3D.

I want this button to move with the platform when it moves, yet here it’s where it gets complicated:

My project uses a raycast-based interaction system. Any objects that I want to interact with need to be on collision layer 2.

As I don’t want to interact with the platform node, I set it only to layer 1.
The GenericButton is on layer 1 and 2.

In game when I activate the button, the platform moves, and so does seemingly the GenericButton, except I notice that seemingly the attached COllusionShape3D of the GenericButton stays in place.
All the other objects seem to move as expected.

This behavior does NOT occur, if I set the platform’s collision to layer 1 and 2.
Unfortunately, if I set my platform like that, my system picks up the whole platform as the interaction trigger, practically making all it’s collision shapes work like the button.

Is there a way to get the GenericButton’s collision shape to move with the rest of it / not have it stay in place for some reason?

Thanks in advance!

PS: I’m ussing tweens to move the platform. And the AnimatableBody3D’s all have Sync to Physics turned on.

[cammymoop]

It looks like the AnimatableBody3D (specifically the button) isn’t syncing it’s new position to the physics server when it’s parent’s transform updates, which is almost certainly a bug.
Anyway if you just pretend to update the inner body’s position it looks like if fixes it:

@onready var starting_pos: = position
func _physics_process(_delta: float) -> void:
	position = starting_pos

it’s too smart for our tricks if we do position = position so I had to save the position from the start and use that so it would actually try saving the position heh.

if you need to be a little more optimal you would want to only do that kind of thing if the plaform is actually moving that frame

edit: it’s this bug CollisionShape does not update moving AnimatableBody3D? · Issue #67257 · godotengine/godot · GitHub
looks like if you just set sync_to_physics off on the internal body (the button) that will also fix it, the collision body might be a frame behind but I doubt that would ever be noticible

[phazorknight]

Oh I see, thanks for this insight!

Actually just turning sync to physics off on the child node (button) worked well for my case.