[vtk-developers] Changes to surface selection in VTK/ParaView

[Utkarsh Ayachit]

Folks,

Wanted to give everyone an heads up on some restructuring with the 
hardware-based surface cell/point selection code. The 
vtkVisibleCellSelector is now replaced by vtkHardwareSelector. 
vtkHardwareSelector can theoretically support selection of any attribute 
  cells/points/vertices/edges/rows etc. (although currently only 
cells/points are supported). We have new selection rendering pass on 
vtkProp named RenderSelectionGeometry() which is called by the renderer 
during selection rendering pass. In this pass, the polydata mapper 
(vtkPainterPolyDataMapper) uses vtkHardwareSelectionPolyDataPainter 
instead of the default painters to do the rendering. Thus now, each 
prop/mapper takes on the responsibility of deciding how to render itself 
during the selection passes (rather than the renderer as was the case 
earlier), thus making it possible for different types of mappers to 
handle selection on their own.

The API on vtkHardwareSelector is similar to vtkVisibleCellSelector 
except that choosing how many passes to render is not decided by the 
vtkHardwareSelector on the fly. Also when selecting points, the stencil 
buffer is no longer needed. vtkHardwareSelector now directly renders 
point ids and identifies them instead of rendering cells and the points 
in that cells (as was the case earlier). Hence we save on 1 extra pass 
when selecting points.

Utkarsh