code: def setPoint(self, i, p):
          
          poly = self.polydata(False)
          poly.GetPoints().SetPoint(i, p)
          poly.GetPoints().Modified()
          # reset actor to identity matrix position/rotation:
          self.PokeMatrix(vtk.vtkMatrix4x4())
          return self
docs: Set specific `i-th` point coordinates in mesh.
          Actor transformation is reset to its original mesh position/orientation.
  
          :param int i: index of vertex point.
          :param list p: new coordinates of mesh point.
  
          .. warning:: if used in a loop this can slow down the execution by a lot.
  
          .. seealso:: ``actor.Points()``