bevy-rust-gpu pipeline

[Shfty]

Need to set up a shader crate and verify that rust-gpu-sdf can be compiled into SPIR-V.

[Shfty]

On deeper workflow:

Since SDFs are heavily-nested rust types, it shouldn't be too hard to pass them across the bevy / shader workspace boundary in textual form via a new types param for permutate-macro, thus eliminating the need to enumerate them via parameter or basic const type when hot-rebuilding.

And since rust-gpu-sdf can be used in both, all manner of interesting CPU-side functionality could be implemented by extending SignedDistanceField with custom attributes.

A few ideas:

• Bake SDFs into regular meshes for setups that don't take advantage of features like high-res curves or dynamic blending
• Generate bevy entity hierarchy by splitting a SDF tree at Union nodes, let the depth buffer handle composition as an optimization
• Nested BVH generation for optimizing start / end distances and traversal during raymarching
• Generating bind group structure and uniform data for injection during material specialization
• Triangulating SDFs into shell meshes for tighter initial-ray rasterization
• Generate composite rapier colliders for an SDF type