reduce vertex number of obj file

decimate.py

from __future__ import print_function
import sys
import vtk

if(len(sys.argv) < 3):
  print('Usage: ', sys.argv[0], 'input.obj', 'output.obj')

reader = vtk.vtkOBJReader()
reader.SetFileName(sys.argv[1])
reader.Update()
obj = reader.GetOutput()

decimate = vtk.vtkDecimatePro()
decimate.SetInputData(obj)
decimate.SetTargetReduction(0.9)
decimate.PreserveTopologyOn()
decimate.Update()

output = decimate.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) )