Represent surface voxels using vtkcubesource

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1

Hi,

I am trying to represent voxels using vtkcubesource and find it very slow in rendering. The number of cubes are approximately around 100k. here is the code snippet.

for( auto k = 0; k<zsteps; ++k)
for(auto j = 0; j<jsteps; ++j)
for(auto i = 0; i<isteps; ++i)
{

        vtkNew<vtkCubeSource> cubesource;
        cubesource->setcenter( center.x, center.y, center.z);
        cubesource->SetXLength(GetStepX());
        cubesource->SetYLength(GetStepY());
        cubesource->SetZLength(GetStepZ());


        vtkNew<vtkPolyDataMapper> icube;
        icube->SetInputConnection(cubesource->GetOutputPort());

        vtkNew<vtkActor> cubeActor;
        cubeActor->SetMapper(icube);   
        
        renderer->AddActor(cubeActor);

}

renderer->ResetCamera();
renderWindow()->AddRenderer(renderer);

This displays the 3d profile but is terribly slow to the point where it is unusable. It takes nearly 5 minutes to render the structure and any further interactions (such as rotate or zoom in/out) with the graph takes about 45s up to a minute.

Since this approach uses one actor and mapper per each cubesource i tried using a single actor and mapper with glyph3d object which also yielded the same result. The rendering was still very slow. Here is the code with single actor and mapper

vtkNew<vtkPoints> points;
vtkNew<vtkPolyData> polydata;
vtkNew<vtkIntArray> scalars;
vtkNew<vtkGlyph3D> glyph3D;

for( auto k = 0; k<zsteps; ++k)
for(auto j = 0; j<jsteps; ++j)
for(auto i = 0; i<isteps; ++i)
{

        points->InsertNextPoint(pcenter.GetX(), pcenter.GetY(), pcenter.GetZ());
        scalars->InsertNextValue(iMaterial);

}

        polydata->SetPoints(points);
            polydata->GetPointData()->SetScalars(scalars);

            vtkNew<vtkCubeSource> cubesource;

            cubesource->SetXLength(GetStepX());
            cubesource->SetYLength(GetStepY());
             cubesource->SetZLength(GetStepZ());

            glyph3D->OrientOff(); // disable orientation
            //glyph3D->SetScaleModeToScaleByVectorComponents(); // sacle along each axis
            glyph3D->SetSourceConnection(cubesource->GetOutputPort());
            glyph3D->SetInputData(polydata);
            glyph3D->Update();

            vtkNew<vtkPolyDataMapper> icube;
            icube->SetInputConnection(glyph3D->GetOutputPort());

            vtkNew<vtkActor> cubeActor;
            cubeActor->SetMapper(icube);

            icube->Update();
            renderer->AddActor(cubeActor);

renderer->ResetCamera();
renderWindow()->AddRenderer(renderer);

The dataset is structured points with unform spacing in 3 dimensions. The dataset is too large for a volumetric rendering. Is there any other datastructure in vtk better suited to our usecase and to help with the rendering slowness in particular. I have looked into vtkimagedata and vtkstructuredpoints but am not entirely sure.

Any help is appreciated.

2

vtkimagedata with geometry rendering

1 Like
3

The dataset is too large for a volumetric rendering.

100K voxels is a tiny volume, volume rendering can easily handle that.

You also might want to try vtkGlyph3DMapper.

Also, as Sebastien suggested, extracting a surface from the volume followed by rendering should be fast.

4

Can you please elaborate a bit or point me to an example

5

It would be helpful to have data, and also provide more information about what you are trying to do; e.g., a sample image etc.