Custom changes for godot-rapier

[Ughuuu]

• Change how interaction groups work to be or instead of and.
• Add custom friction rules needed for godot symetry Feature: Add support for custom friction and bounce CombineRules dimforge/rapier#622

[ThierryBerger]

It's a change we can consider for rapier, an example showcasing the kind of new setup this PR enables would help with upstreaming it 🤩

Also, extra care should be taken to avoid breaking a previously possible setup, which is difficult to assess here. a "migration guide" will probably be welcome.

To clarify, I'm not requesting these (hey it's your fork, thanks for making this in the open 😄), I'm voicing my interest and discussing a possible path forward for rapier 👍.

[Ughuuu]

Thanks for comments. The main problem currently with godot-rapier is in order to integrate into godot physics it needs to work in same way.

Friction and bounce works differently in rapier vanilla, this just makes it work same way as in godot. I could show examples or reference how it works in godot, but not sure if rapier would want to change its behaviours because godot does something in a specific way.

Layers and masks also work differently in godot. Collisions happen with an or instead of and, but it's a bit more complicated also. Godot also has asymetrical collisions. Meaning if A has layer 1 but no mask and B has layer 1 and mask 1, B will collide with A but A will not collide with B. https://docs.godotengine.org/en/stable/tutorials/physics/physics_introduction.html#collision-layers-and-masks

• Now, on this, however could we implement this? Idk, godot jolt what does is it gives object A infinite mass and inertia in the collision so it seems like it doesnt interact.

Probably right now godot rapier is not big enough to say something like: this is how it works, deal with it. People aren't going to change their project in godot to work with different way godot rapier works. So for now at least, having some local changes might be expected, again unless rapier is willing to add them to rapier vanilla.

[ThierryBerger]

• For the interaction groups ||, I'll mention Add InteractionGroups::test_or, increase to 64 bits dimforge/rapier#170 which adds an opt-in for this change.

[Ughuuu]

Perfect, if that gets in I can remove some parts of this.