[Paraview] Disappearing volume rendering?

[Cory Quammen]

Bertwim,

I'm not sure that the volume renderer can handle VTK_HEXAHEDRON
elements. Try the "Tetrahedralize" filter on your source and see if
the Volume representation works.

Thanks,
Cory

On Mon, Oct 13, 2014 at 10:19 AM, B.W.H. van Beest <bwvb at xs4all.nl> wrote:
> Hi,
>
> I'm struggling to get a proper 3D view of my model system (yes,
> embarrassing!)
> but must admit my defeat.
> After stripping almost everything, keeping the minimum to exhibit the
> issue,
> I'm left with the following:
>
> I have created a simple box source. To get a 3D representation, I
> sub-classed
> the code for this Source from vtkUnstructuredGridAlgorithm.
>
> In the RequestData method, I define the 8 point of the unit cube. I
> added the points to the
> underlying unstructed grid, and I specified the cell topology.
>
> This all seems to work: when instantiating this box Source, I *do* get the
> expected cube in the representations (Surface, wireframe, Points).
>
> However, when I select the "Volume" representation, *the image disappears*
> What am I doing wrong?
>
> As the code is not too long and very simple, I take the freedom to paste
> it below.
>
> Kind regards.
> Bertwim
>
> =========================================
>
>  int sphBoxSourceC::RequestData( vtkInformation *vtkNotUsed(request),
>                                 vtkInformationVector
> **vtkNotUsed(inputVector),
>                                 vtkInformationVector *outputVector)
> {
>    // Get the info object
>    vtkInformation *outInfo = outputVector->GetInformationObject(0);
>    vtkUnstructuredGrid *umesh = vtkUnstructuredGrid::SafeDownCast(
> outInfo->Get( vtkDataObject::DATA_OBJECT() ) );
>
>    // Pre-allocate some memory
>    umesh->Allocate( 1024 );
>
>    // Specify points.
>    double r0[] = { 0.0, 0.0, 0.0 };
>    double r1[] = { 1.0, 0.0, 0.0 };
>    double r2[] = { 0.0, 1.0, 0.0 };
>    double r3[] = { 1.0, 1.0, 0.0 };
>    double r4[] = { 0.0, 0.0, 1.0 };
>    double r5[] = { 1.0, 0.0, 1.0 };
>    double r6[] = { 0.0, 1.0, 1.0 };
>    double r7[] = { 1.0, 1.0, 1.0 };
>
>    // Collect the points in a vtk data structures.
>    {
>       vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New();
>       points->SetDataType( VTK_DOUBLE );
>
>       points->InsertNextPoint( r0 );
>       points->InsertNextPoint( r1 );
>       points->InsertNextPoint( r2 );
>       points->InsertNextPoint( r3 );
>       points->InsertNextPoint( r4 );
>       points->InsertNextPoint( r5 );
>       points->InsertNextPoint( r6 );
>       points->InsertNextPoint( r7 );
>
>       // Transfer points to umesh.
>       umesh->SetPoints( points );
>    }
>
>    // Cell Topology
>    vtkIdType vtx[8] = { 0, 1, 3, 2, 4, 5, 7, 6 };
>    umesh->InsertNextCell( VTK_HEXAHEDRON, 8, vtx );
>
>    return 1;
> }
>
>
>
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