None of these helped me so I eventually figured out the best way to get my data into Blender. It doesn’t use VTK but it works - AND IT WORKS ON WINDOWS, which literally seems to not exist anywhere in the internet (I spent 5 hours researching!!!).
Run this code in Blender Python:
(the variable rhoVolume is a dataset in the HDF5 file)
import openvdb as vdb
import h5py
import os
workingFolder="C:/Path/To/Your/File/"
h5_path = os.path.join(workingFolder, "Test10.h5")
vdb_path = os.path.join(workingFolder, "Test10.vdb")
f=h5py.File(h5_path,'r+')
key=list(f.keys())[0]
data = f["rhoVolume"][()]
grid = vdb.FloatGrid()
grid.copyFromArray(data)
grid.name = "rhoVolume"
vdb.write(vdb_path, grids=[grid])
print("VDB saved!!")
This works on Windows 10, with Blender 4.4.3 as of June 2025. Looks like Blender has openvdb compiled within itself, which means you just need to get the data in the Blender Python. I’m sure you can figure out how to do it in VTK too, but I’m honestly completely gassed out and annoyed I spent so much time on this. Hopefully this helps somebody in the future…