CSGShape doesn't have physics material

[Saitodepaula]

Godot version:
3.2 Stable

OS/device including version:
Windows 10 Home

Issue description:
I think it is not a bug exactly, but the way CSGShape is designed. But in the way it is now, it doesn't have a physics material, although the docs says it will act like a static body if use_collision is on.

I understand that, as prototype tool, maybe a physics material is not needed. But there is no easy way to create a mesh out of a CSGShape, and reading #19232, it looks like CSGs need more features to be actually useful as prototype tools.

So, all this considered, I think that the fact the engine lets you easily add a collision shape leads the user to think that a physics material is possible.

Also, where is the collision shape added when you click use_collision and how can it be accessed? Because a raycast only intercepts the CSGShape (see below, step 5), shouldn't it be intercepting a physics body?

Steps to reproduce:

1. Add a path, add some points to get a shape
2. Add a CSG Polygon as child of paht. Set mode to path, and path node to the parent path. Set Use Collision on
3. Add a Raycast, place it in a way it intersects the CSG Polygon
4. Add a script to the raycast, and in the func _process(delta) add print(self.get_collider()) and print(self.get_collider().get_physics_material_override())
5. Run. It will print [CSGPolygon:XXXX] and then an error of non existent function for get_physics_material_override()

Minimal reproduction project:
CSGStaticBodyTet.zip

[Zireael07]

I just tried to use a CSG polygon as a tunnel, and in spite of checking use collision, my cars aren't colliding with it, not in 3.2 and not in 3.2.1 rc1. So use_collision seems weird either way.

[Calinou]

@Zireael07 Can you take a screenshot of the tunnel with Debug > Visible Collision Shapes enabled?

[Zireael07]

Done :)
No collision shape visible.

[Zireael07]

I found a workaround, basically this: #19232 (comment) and body.create_trimesh_collision() (from code) or Mesh -> Create Trimesh Static Body (in editor) but use_collision seems broken on 3.2 stable onwards.

[Calinou]

@Zireael07 Can you reproduce this in any 3.2 alphas/betas/RCs? You can download them here.

[Zireael07]

Same problem in beta1 (and all subsequent betas).

Beta 1 :(

Alphas throw a hissy fit about indentation in one of the other files, and as far as I can see the line in question has no spaces but tabs, so IDK what their problem is.

I copied just the csg scene to a new project, opened it in alpha 1, and well... no collision shapes shown. (Making some sort of a character to check if it clips would take more time than I currently have, sorry)

[Zireael07]

(I realize we've essentially hijacked someone else's bug report, but it looks like they're connected extremely close - alternately, I think you people can move bug reports around? I unfortunately can't...)

[Saitodepaula]

@Zireael07 hehe, it's fine for me. Like I said, I'm not sure it is a bug I have reported, more a matter of features that are not there by design, but would be extremely useful.

[madmiraal]

Related to #22246.

[lexum0]

I made this tool plugin to work in the meantime with Physics Materials using CSG nodes in case anyone is interested

https://github.com/lexum0/CSGExport-Godot

[Calinou]

Closing in favor of godotengine/godot-proposals#7568, as feature proposals are now tracked in the Godot proposals repository.