vtk2obj.py

import sys

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

import vtk

reader = vtk.vtkUnstructuredGridReader()
reader.SetFileName(sys.argv[1])
reader.Update()
output = reader.GetOutput()

out_obj_file = sys.argv[2]
with open(out_obj_file, 'w') as f:
  for i in range(output.GetNumberOfPoints()):
    pt = output.GetPoint(i)
    f.write('v %.5f %.5f %.5f\n' % (pt[0], pt[1], pt[2]))

  for i in range(output.GetNumberOfCells()):
    cell = output.GetCell(i)
    f.write('f %d %d %d\n'% (cell.GetPointId(0)+1, cell.GetPointId(1)+1, cell.GetPointId(2)+1) )