[Paraview] RE: [vtk-developers] Integrating new volume renderer into VTK/Paraview

[Moreland, Kenneth]

> For integration with VTK, we see the following issue: Our 
> code requires the most recent OpenGL extension header files.  
> VTK currently uses headers that are slightly out of date.  
> The newest headers are always available at the SGI website 
> (http://oss.sgi.com/projects/ogl-sample/registry/).

I'll take the action item to do this.

> For complete integration with ParaView, we see the following issues:
> 1.  We do not understand ParaView's LOD selection.  Thus, we 
> have not incorporated our LOD technique inside ParaView.  We 
> would appreciate getting help from someone that knows the 
> details of how this works.

ParaView defines 2 levels of detail.  The low level of detail renders
fast for mouse interaction.  The high level of detail renders a full
resolution.

In the current implementation, a surface rendering is performed for low
levels of detail and a volume rendering (either PT or ZSweep depending
on user selection) is performed for high levels of detail.  Since HAVS
has built in LOD, we can change the behavior to use that mapper for both
levels of detail while toggling a parameter in the mapper.

> 2.  Although our code works on both ATI and NVidia, ParaView 
> does not seem to use hardware-acceleration on machines with 
> ATI cards.  Even with the precompiled Windows binaries from 
> the web, the PT algorithm is extremely slow, indicating that 
> hardware rendering is not being used.  
> Is this an intrinsic limitation of ParaView?

No.  The PT mapper uses nothing that is not part of the OpenGL 1.1
standard.  The source for the PT mapper is in
ParaView/VTK/VolumeRendering/vtkProjectedTetrahedraMapper.cxx.  If you
have a chance, try commenting out pieces of code until the PT algorithm
performs as you expect.  Maybe the code is somehow touching some feature
not supported by the card and forcing it into software mode.

-Ken