Convert vtkUnstructuredGrid VTK file to Wavefront OBJ file or STL file

vtkToObj.py

#!/bin/env python3
# Convert vtkUnstructuredGrid VTK file to Wavefront OBJ file or STL file

import sys
import os
import vtk

if len(sys.argv) != 3:
  print('Usage: ', sys.argv[0], 'in.vtk out.obj')
  sys.exit()

infile = sys.argv[1]
outfile = sys.argv[2]
outext = os.path.splitext(outfile)[1]

# read VTK file
reader = vtk.vtkUnstructuredGridReader()
reader.SetFileName(infile)
reader.Update()
obj = reader.GetOutput()
print(obj)

# convert unstructured mesh
geofilter = vtk.vtkGeometryFilter()
geofilter.SetInputData(obj)
geofilter.Update()

obj = geofilter.GetOutput()

print("Writing", outext)
if outext == ".obj": # write OBJ
  writer = vtk.vtkOBJWriter()
  
if outext == ".stl": # write STL
  writer = vtk.vtkSTLWriter()

writer.SetFileName(outfile)
writer.SetInputData(obj)
writer.Write()