Unfortunately, the STL file format itself doesn't support more than one object, see: http://en.wikipedia.org/wiki/STL_(file_format) -- View this message in context: http://vtk.1045678.n5.nabble.com/how-to-write-2-solids-vtkPolyData-into-1-stl-tp5725556p5725576.html Sent from the VTK - Users mailing list archive at Nabble.com.