code: def triangle(self, verts=True, lines=True):
          
          tf = vtk.vtkTriangleFilter()
          tf.SetPassLines(lines)
          tf.SetPassVerts(verts)
          tf.SetInputData(self.poly)
          tf.Update()
          return self.updateMesh(tf.GetOutput())
docs: Converts actor polygons and strips to triangles.