Convert color mesh to VDB

[chrisflesher]

I am looking for advice on how to convert a high resolution mesh to surface / color VDB.

My current solution is to:

1. Use a python script to generate surface / color VDB
2. Display images from it using vdb_render and exrdisplay

However this method is very slow. Some other options I considered:

1. Use AX but I couldn't find any kind of nearest neighbor functionality?
2. I could re-write this using C++ but wasn't sure if OpenVDB already has some kind of nearest neighbor functionality that would work for this already?
3. Maybe the best case scenario is that a tool for this already exists (preferably free)

[chrisflesher]

Here's the python script.

import meshio
import numpy as onp
import pathlib
import pyopenvdb as vdb
import scipy.spatial
import tqdm

ply_path = pathlib.Path.home() / 'mesh.ply'
resolution = 0.02

# Create surface grid
mesh = meshio.read(str(ply_path))
surface_grid = vdb.FloatGrid.createLevelSetFromPolygons(
    points=mesh.points,
    triangles=mesh.cells_dict.get('triangle', None),
    transform=vdb.createLinearTransform(voxelSize=resolution),
    halfWidth=3)
surface_grid.name = 'surface'

# Create color grid
kdtree = scipy.spatial.KDTree(mesh.points)
color_grid = vdb.Vec3SGrid()
color_grid.name = 'color'
color_grid.transform = surface_grid.transform
color_grid_accessor = color_grid.getAccessor()
for item in tqdm.tqdm(surface_grid.citerOnValues(), total=surface_grid.activeLeafVoxelCount()):
    if item.count == 1:
        point = onp.array(item.min) * resolution  # TODO: improve this position to be on the surface...
        _, nearest_neighbor_index = kdtree.query(point, k=1)
        red = float(mesh.point_data['red'][nearest_neighbor_index])
        green = float(mesh.point_data['green'][nearest_neighbor_index])
        blue = float(mesh.point_data['blue'][nearest_neighbor_index])
        color_grid_accessor.setValueOn(item.min, (red, green, blue))

# Write the result to disk
vdb_path = ply_path.with_suffix('.vdb')
vdb.write(str(vdb_path), [surface_grid, color_grid])