BeepCube: Cut particles, refactored shader, cut physics etc...

[Firepal]

• BeepCube material was almost half-rewritten:

  • Cut white-margin rotation is done using a rotation matrix instead of raw arithmetic and if-statements. (Previous method also exhibited some strange artefacts..)
  • Moved cut white-margin rotation code from pixel shader to vertex shader.
  • Use discard call for alpha scissoring.
  • Removed excess uniforms from SpatialMaterial conversion process.
  • Re-organized the shader for readability.

• The rigid body forces applied to the cutted cube halfs no longer uses the cutplane variable. Instead we use the 2D cutplane (also used to compute the "cut angle").

  • This is less accurate than using cutplane, but it's prettier, and I couldn't find out how to use it to generate a rotation matrix. I also added side-forces to really split the halfs apart.

• Slicing a cube now makes cool particle effects show up! One particle effect is radial, and the other follows the cut direction.

[NeoSpark314]

With this change I now get black cubes (Quest 1) also on desktop visible; do you maybe know what might cause this?

I don't have time right now to investigate but hopefully later.

[Firepal]

I think the BeepCube texture isn't set in the material, I was sure of it though? I'm gonna check

[Firepal]

Uh, looks fine...

[NeoSpark314]

This is how it looks for me on desktop right now with master:

Maybe it's a problem with my godot version; but for Quest export I use the included .apk;

[NeoSpark314]

Now it works for me; I had some changes due to testing the previous PR merges locally I missed; git checkout . helped:

Thx for this nice contribution!!

[Firepal]

Aha, git can be silly sometimes :)