[Paraview] volume rendering/ isosurfaces from a adaptive subset of a regular grid.

[Daniel Goldstein]

Lisa Avila wrote:

> Hi Daniel,
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>> 1)  Are hexahedral grid elements the only type supported for 
>> unstructured volume rendering and isosurfaces?
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> Actually, I believe all the unstructured grid volume rendering methods 
> currently work on tetra - so ParaView automatically tetrahedralizes 
> your data for you before rendering.

 Ok. I can generate hexahedral elements fairly easily from my data. What 
is the overhead for ParaView to "automaticly tetrahedralizes" the data?
If it is low then it is best for me to make hexahedra and let ParaView 
make tetrahedra from them. Does this sound like a reasonable plan?

>
>> 2) Do the faces of the hexahedral elements need to be contiguous? 
>> (i.e.. can four small faces meet up with one large face?)
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> The tetrahedral model can be an arbitrary set of tetrahedra.

 Ok this relates to the response above.  If I generate hexahedra such 
that a face never mates with more then one face but
mutiple small faces can match to a larger face, will Paraview be able to 
make a clean tetrahedral grid from it that will
make good isosurfaces without cracks and holes?  I want to understand 
the consequences of how I generate the grids before hand.

>
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>> 3) Is there any limit on the number of  unstructured grid elements 
>> that can be volume rendered with ParaView?
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> Yes - the current version cannot handle large grids (large being more 
> than maybe a few hundred thousand elements) because of the memory 
> overhead of the method. Sandia has a nice hardware projection 
> technique which is being incorporated in ParaView now - this will 
> handle much larger grids  and will be much faster than the current 
> method.

 
   Can you point me to a reference to this project. I am interested in 
what hardware they are using (so I can see if I can get access to the 
same hardware..)


   Thanks a million for the help!  I'm impressed with ParaView so far!

Dan

>
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>> 4) I noticed that KitWare has a phase 1 SBIR for working on AMR 
>> visualization. Will this code end up in ParaView?
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> If we get a Phase II it is likely to show up in ParaView. This is not 
> likely to happen very soon - if we get Phase II the funding would not 
> start until January I believe. However, the base classes will be in 
> VTK within the next month or so.
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> Lisa
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