The modeling PolyData class is used to represent a PolyData solid       
model.                                                                  

compute_boundary_faces(angle)  
   
   Compute the boundary faces for the solid model. 
   
   This method needs to be called when creating new PolyData or reading in  
   models that don't have faces already defined (e.g. models derived from   
   STL data). It does not need to be called for OpenCascade or Parasolid    
   models.
   
   For PolyData models faces are distinguished using the angle of the       
   normals between adjacent triangles. If the angle is less than or equal   
   to the 'angle' argument then the triangles are considered to part of     
   the same face. 
   
   Args: 
     angle (float): The angle used to distinguish faces in a model.         
   
   Returns list([int]): The list of integer face IDs. 

get_face_ids()  
   
   Get the model face IDs. 
   
   Face IDs identify the boundary faces representing the solid model. They  
   are used to identify a face for certain operations (e.g. get_face_polydata). 
   
   Returns list([int]): The list of integer face IDs. 

get_face_polydata(face_id)  
   
   Get the polydata geometry for a face.  
   
   Args: 
     face_id (int): The face ID. 
   
   Returns (vtkPolyData object): The vtkPolyData object containing the face geometry.  

get_polydata()  
   
   Get the polydata geometry for the model.  
   
   Returns (vtkPolyData object): The vtkPolyData object containing the model geometry.  

set_surface(surface)  
  
  Set the PolyData surface defining the model. 
  
  Args: 
    surface (vtkPolyData): The vtkPolyData object representing the surface. 

write(file_name, format)  
   
   Write the solid model to a file in its native format. 
   
   The native formats supported for each modeling kernel are: 
   
         OpenCascade: brep 
   
         Parasolid: xmt_txt 
   
         PolyData: ply, stl, vtk and vtp  
   
   Args: 
     file_name (str): The name in the file to write the model to. 
     format (str): The native format to write the model to.