Add vtkDataSetRegionSurfaceFilter to VTK.
Like vtkDataSetSurfaceFilter, vtkDataSetRegionSurfaceFilter is a filter that extracts the surface from a dataset. Unlike vtkDataSetSurfaceFilter, the filter accepts integer cell data to denote regions; the regions are then used as an additional criterion for determining surfaces.
This filter has been ported from ParaView's VTKExtensions.