Voxel grid shortcuts

This might be nice and fast if it worked right. Voxel grid shortcuts: precompute closest full cells for cell-cell-pairs, look up ray entry & exit cells, jump ray to closest cell. On exit, jump ray out of the model. 🤔

But does it make sense to swap 4 steps through a 512 element 8x8x8 acceleration structure for some math & a lookup from a 262k element shortcut list 🤔

If you do only the external faces, 64^3 grid => 6^2x64^2 accel, which might be worthwhile.

The problem in the above screenshots is that a voxel-to-voxel beam intersects more voxels than a ray would. Now it's generating the shortcuts by tracing a ray from the center the start voxel to the center of the end voxel to find the closest filled voxel the ray intersects. Which doesn't visit all the voxels a beam would, so you get gaps in the model. And my code is broken in other ways, eh.