gizmo.add_collision_triangles() & gizmo.add_collision_segments() Only Work When add_mesh() Is Called

[Kalcen]

Godot version

v4.0.beta4.official [e675154]

System information

Windows 10

Issue description

I noticed that add_collision_triangles() and/or add_collision_segments() only work if add_mesh() is used in the same _redraw(gizmo): function. I don't want to render a mesh, so I guess I could make the material not render at all, but I would still like to have a selectable collider for the gizmo.

Steps to reproduce

Download the plugin, enable it, and place a Test Node into a 3D scene. The gizmo.add_mesh() function is located in the test_gizmo_plguin.gd script. If you comment it out, the gizmo's collider mesh is no longer selectable in the scene view.

Minimal reproduction project

gizmo_selection_issue.zip

[Calinou]

Related to #53083.

[TomCatFort]

This issue caused me quite the headache.
Many thanks for @Kalcen for finding a workaround with add_mesh() and an invisible material.

I also noticed that the added workaround mesh needs to 'contain' or 'cover' the triangle mesh, otherwise the parts of the triangle mesh that are outside of the workaround mesh remain unselectable.
I assume, the engine first checks if the workaround mesh itself is clicked on, and only then checks the triangle mesh itself.

[juanjp600]

I decided to look into this and come up with a fix. The MRP given here appears to work correctly with #94553 applied when the add_mesh call is removed.