[Paraview] Can Use Volume Vis with Cell Data?

[Utkarsh Ayachit]

For volume rendering image data, ParaView uses 
vtkFixedPointVolumeRayCastMapper and that mapper does not support using 
cell data scalars. Hence ParaView complains.

Utkarsh

Kent Eschenberg wrote:
> Any suggestions would be welcome.
> 
> Kent Eschenberg wrote:
>> The CVS version from May allows the representation to be changed to 
>> volume for a vti file with only float cell data.
>> But then it shows the message "Cannot volume render since no point (or 
>> cell) data available." which is incorrect.
> 
> 
> This morning I updated my version from CVS but the problem persists. The 
> messages comes from this section of code in 
> pqPipelineRepresentation::onRepresentationChanged:
> 
> ======
>  // Representation is Volume, is color array set?
>  QList<QString> colorFields = this->getColorFields();
>  if (colorFields.size() == 0)
>    {
>    qCritical() <<      "Cannot volume render since no point (or cell) 
> data available.";
>    this->setRepresentation(vtkSMPVRepresentationProxy::OUTLINE);
>    return;
>    }
> ======
> 
> What are these "color fields"? Why are they missing when using cell 
> data? Why does the message say there is no data when its actually the 
> "color fields" that are missing?
> 
> The variable "Dummy" can be used to color the surface of both 
> attachments, cubePointInt32.vti and cubeCellInt32.vti. Switching to 
> volume visualization works for the first (point data) but produces the 
> above error for the second (cell data).
> 
> TIA!
> Kent
> Pittsburgh Supercomputing Center
> 
> 
> ------------------------------------------------------------------------
> 
> <?xml version="1.0"?>
> <VTKFile type="ImageData" version="0.1" byte_order="LittleEndian">
>  <ImageData WholeExtent="0 2 0 2 0 2" Origin="0 0 0" Spacing="0.5 0.5 0.5">
>   <Piece Extent="0 2 0 2 0 2">
>    <CellData Scalars="Dummy">
>     <DataArray Name="Dummy" type="Int32" format="ascii">
>      0 0 0 0
>      100 0 0 0
>     </DataArray>
>    </CellData>
>   </Piece>
>  </ImageData>
> </VTKFile>
> 
> 
> ------------------------------------------------------------------------
> 
> <?xml version="1.0"?>
> <VTKFile type="ImageData" version="0.1" byte_order="LittleEndian">
>  <ImageData WholeExtent="0 2 0 2 0 2" Origin="0 0 0" Spacing="0.25 0.25 0.25">
>   <Piece Extent="0 2 0 2 0 2">
>    <PointData Scalars="Dummy">
>     <DataArray Name="Dummy" type="Int32" format="ascii">
>      0 0 0 0 0 0 0 0 0
>      0 0 0 0 100 0 0 0 0
>      0 0 0 0 0 0 0 0 0
>     </DataArray>
>    </PointData>
>   </Piece>
>  </ImageData>
> </VTKFile>
> 
> 
> ------------------------------------------------------------------------
> 
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