Make revoxelization on GPU faster about fluidx3d

[ProjectPhysX]

Hi @trparry, thanks for the post! I am planning to replace the current slow voxelization, there is much faster algorithms on the internet. The two solutions I have currently implemented are not optimal:

• voxelize_stl_hull is on CPU and rather fast with N^2 scaling, but only voxelizes the hull and sometimes there are holes
• lbm.voxelize_stl is on GPU, but it's the slow ray-cast approach that scales with N^5, where only N^3 can be parallelized

Ideally the voxelization should be way faster than an LBM time step, so coupled fluid + rigid body simulations work much faster.

I'll leave this issue open as a reminder for myself to implement it some time :)

[ProjectPhysX]

Done! I found a quite ingenious solution that speeds up GPU voxelization by about 500x, reducing runtime from minutes to milliseconds. Details are in the v2.1 release notes.

[trparry]

This is awesome. Thank you!

[Antotabo]

Remesh in milliseconds 😱. This is great news ! Congrats on all this good work. My dream of creating a sandbox toy with rigid body/fluid interaction now seems more than feasible. Think Algodoo meets Powder Toy.