Add Gizmo to display 3D custom AABB

[CrayolaEater]

This PR adds the ability to preview the custom AABB of a MeshInstance3D inside the editor.

[Calinou]

Tested locally (rebased on top of master a7b8602), there are issues with the gizmo shape not being updated when you change the Custom AABB property in the editor:

simplescreenrecorder-2024-04-09_18.38.56.mp4

The gizmo only updates if the mesh resource is changed or if you deselect and reselect the node.

The error message spam when changing Custom AABB if no mesh is assigned also applies to master, so it's not specific to this PR: #86369 (comment)

[CrayolaEater]

Tested locally (rebased on top of master a7b8602), there are issues with the gizmo shape not being updated when you change the Custom AABB property in the editor:

simplescreenrecorder-2024-04-09_18.38.56.mp4

The gizmo only updates if the mesh resource is changed or if you deselect and reselect the node.

Yes but I think this is the limitation of the gizmo. I don't really know how to make it update automatically.

[Calinou]

Yes but I think this is the limitation of the gizmo. I don't really know how to make it update automatically.

You can force a gizmo update when the property is changed by calling update_gizmos() at the end of GeometryInstance3D::set_custom_aabb():

godot/scene/3d/visual_instance_3d.cpp

Lines 374 to 380 in 6c57928

	void GeometryInstance3D::set_custom_aabb(AABB p_aabb) {
	if (p_aabb == custom_aabb) {
	return;
	}
	custom_aabb = p_aabb;
	RS::get_singleton()->instance_set_custom_aabb(get_instance(), custom_aabb);
	}

[CrayolaEater]

Yes but I think this is the limitation of the gizmo. I don't really know how to make it update automatically.

You can force a gizmo update when the property is changed by calling update_gizmos() at the end of GeometryInstance3D::set_custom_aabb()

Thanks for the tip!

[Calinou]

Tested locally (rebased on top of master 3b18061), it works as expected.

Note to others: The gizmo is only displayed when the node is selected, so it won't be too intrusive in complex 3D scenes.

[clayjohn]

Looks great to me! I just left a suggestion to fill in the docs. We like to have documentation whenever we add a new feature.

The final step before merging is to squash all the commits together so that the whole PR only contains 1 big commit with all your changes. We like to merge one commit at a time to keep the git history clean and navigable.

If you don't know how to do that, we have a helpful tutorial in the official documentation https://docs.godotengine.org/en/latest/community/contributing/pr_workflow.html#the-interactive-rebase

[akien-mga]

Thanks!