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

[Steven Callahan]

Lisa Avila wrote:

>
> Hi Steve,
>
> Can you send me the code? (either point me to an ftp location or I can 
> give you instructions for uploading files here) We'll look it over 
> here, see what we may need to do on the OpenGL header issues (are you 
> using the vtkOpenGLExtensionManager to manage the use of your 
> extensions and get the function pointers?) It shouldn't be too hard to 
> get this into VTK.
>
Yes, I am using the vtkOpenGLExtensionManager.  More specifically, my 
code works if you update VTK/Utilities/ParseOGLExt/header/*.h with the 
latest from the SGI website.  Thus, incorporating my code would also 
require that the three OpenGL headers in this directory are up to date.

> For ParaView, we are currently using a 2 level LOD method with 
> Projected Tetras being the "fast" one always, and either no second 
> level, or ZSweep or the ray caster for final rendering. This would 
> probably be different in that we would replace PT whenever possible 
> with this new method (as long as the required extensions were 
> available). We can worry about this once the class is integrated into 
> VTK.
>
I understand that PT is being used during interaction.  What I am really 
interested in is rendering datasets larger than a million tetrahedra.  
In this case, the LOD seems to go into a boundary only rendering.  
Instead, I would like to use my volume rendering class with the LOD 
turned on, which basically samples the geometry inside and provides a 
better LOD than what is currently being used (see "Interactive Rendering 
of Large Unstructured Grids Using Dynamic Level-of-Detail.", Vis 2005).

Thanks.

Steve



> Thanks,
>
> Lisa
>
>
>
> At 01:20 PM 12/8/2005, Steven Callahan wrote:
>
>> We are working on integrating the Hardware-Assisted Visibility 
>> Sorting (HAVS) volume renderer into VTK and ParaView.  We have a 
>> prototype version that performs at about twice the speed of  
>> Projected Tetrahedra with about the same image quality as ZSweep, 
>> incorporated into ParaView.  (ZSweep has much better image quality 
>> than PT.)
>>
>> We would like to know what steps we need to take to get this added to 
>> VTK and ParaView.
>>
>> Our implementation is a new volume mapper 
>> vtkHAVSUnstructuredGridVolumeMapper that can be used in place of any 
>> of the other unstructured grid volume mappers.  The actual code 
>> consists of the mapper class along with several shader files which 
>> are written in ARB assembly and work with ATI and NVidia video 
>> cards.  The code also supports a new high quality, dynamic 
>> Level-of-Detail approach by passing in a desired frame rate...
>>
>> 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/).
>>
>> We have integrated our code into ParaView.   For screenshots 
>> comparing PT with HAVS, see http://www.sci.utah.edu/~stevec/images.
>>
>> 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.
>> 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?
>>
>> Any help or advice on getting this code into VTK and ParaView would 
>> be helpful.  Thanks
>>
>> Steve Callahan and Claudio Silva
>>
>> PS. We also have an efficient software volume renderer based on the 
>> same algorithm that we would like to incorporate in the near future.
>>
>>
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>
>
>