Voxelize STL file?

Question

Basically, i have a corpus of ~10,000 STL files, and i need to turn them all into 32x32x32 arrays of 1's and 0's (voxels)

I already have this script that turns STL files into voxels; https://github.com/rcpedersen/stl-to-voxel , but sometimes even though i specify that i need a 32x32x32 array, it will give me some huge array, and also along with being buggy, it takes FOREVER (processed ~600 files in 48 hours...)

Would it be easier to attempt to fix this script, or to write my own? It doesnt seem like voxelizing an STL would be a hard task, but I don't know any of the methods out there for this; if there are any strategies/tips, anything would be greatly appreciated.

Answer 1

Sorry to be a bummer, but voxelisation is actually quite a hard task. And not something Python is suitable to do quickly. Even for the simple slice/crossing test I would think a c++ implementation will beat python 1:100. I recommend libigl. Or do it on the GPU for realtime :) Look for conservative rasterization. But that is for "good" meshes that are non intersecting and closed. Otherwise it becomes a lot harder. Look for "generalized winding numbers" - also in igl.

Answer 2

Basicly voxelizing facet surface means separation inside form outside. It can be done in different ways: easiest way is to find signed distance from each voxel but it requeres input mesh to be closed, other way is to find winding number. You can find implemetation of both in MeshLib. Also there is python module that can help you:

pip install --upgrade pip
pip install meshlib

from meshlib import mrmeshpy as mm

# load mesh
mesh = mm.loadMesh(mm.Path("path_to_file.stl"))

mtvParams = mm.MeshToVolumeParams()
# signed will have negative values inside mesh and positive outside, but requires closed mesh
mtvParams.type = mm.MeshToVolumeParamsType.Signed
# voxels with presice distance - 3 inside, 3 - outside
mtvParams.surfaceOffset = 3

# find correct voxel size to have 32x32x32 volume
meshBox = mesh.computeBoundingBox()
boxSize = meshBox.max-meshBox.min
mtvParams.voxelSize = boxSize / 27.0
voxels = mm.meshToVolume(mesh,mtvParams)

# save voxels as tiff slices
vsParams = mm.VoxelsSaveSavingSettings()
vsParams.path = "save_voxels_dir"
vsParams.slicePlane = mm.SlicePlane.XY
mm.saveAllSlicesToImage(voxels,vsParams)