[vtkusers] Memory problem (coloring >44000 tetrahedrons objects)

[ksm-pb at ipt.rwth-aachen.de]

Hello vtkusers mailing list,

i ve a problem with the memory usage of my VTK application. I create more
than 44000 tetrahedron objects which each have to have a different color
and i hope someone can help here.

The 44000 vtkTetra objects are no problem as long as i put all of them into
the same vtkUnstructuredGrid object and using the same color for each
tetrahedron like this:

// iCons contains the indexes for the tetrahedron point connectivities
int * const * iCons = GetCons();
int iNumofPoints = GetNumOfPoints();

vtkUnstructuredGrid * pUnsGrid = vtkUnstructuredGrid::New();
vtkPoints * pPoints = vtkPoints::New();

... // Feeding pPoints from an external data format (10327 coords in my
app)

pUnsGrid->Allocate(iNumOfPoints, iNumOfPoints);
pUnsGrid->SetPoints(pPoints);

for (int i = 0; i < iNumOfTetra; ++i) {
      vtkTetra * pTetra = vtkTetra::New();
      vtkIdList * pTetraIdList = pTetra->GetPointIds();

      for (int j = 0; j < 4; ++j)
            pTetraIdList->SetId(j, iCons[j][i]-1); // iCons knows which IDs
to set for each tetrahedron!

      pUnsGrid->InsertNextCell(pTetra->GetCellType(), pTetraIdList);
}

vtkOpenGLActor * pActor = vtkOpenGLActor::New();
vtkDataSetMapper * pMapper = vtkDataSetMapper::New();
pActor->SetMapper(pMapper);
pActor->GetProperty()->SetColor(1,0,0);
pActor->SetScale(.1,.1,.1);
pMapper->SetInput(pUnsGrid);

This solution works okay with about 30MB of RAM usage, but each tetrahedron
has the same color (1,0,0) now. BUT however if i want each tetrahedron to
have a different color i would have to create for each 44000 tetrahedrons
its own vtkUnstructuredGrid, vtkOpenGLActor and vtkDataSetMapper objects.
So i got at least 44000 * 3 = 132000 more objects in the memory. This way
the app would consume more than 2GB of RAM (and its swapping about 100MB)!
Also the display speed with the vtkOpenGLRenderer gets very very slow! The
code is like this:

int i NumOfTetras = GetNumOfTetras();
std::vector< vtkOpenGLActor* > vecActors;
vecActors.resize(iNumOfTetras);

for (int t = 0; t < iNumOfTetras; ++t )
      vtkPoints * pPoints = GetTetraPoints(t);
      vtkUnstructuredGrid * pUnsGrid = vtkUnstructuredGrid::New();

      pUnsGrid->Allocate(4, 4);
      pUnsGrid->SetPoints(pPoints);

      vtkTetra * pTetra = vtkTetra::New();
      vtkIdList * pTetraIdList = pTetra->GetPointIds();

      for (int j = 0; j < 4; ++j)
            pTetraIdList->SetId(j, j);

      pUnsGrid->InsertNextCell(pTetra->GetCellType(), pTetraIdList);

      vtkOpenGLActor * pActor = vtkOpenGLActor::New();
      vtkDataSetMapper * pMapper = vtkDataSetMapper::New();
      pActor->SetMapper(pMapper);
      pActor->GetProperty()->SetColor(GetTetraColor(t));
      pActor->SetScale(.1,.1,.1);
      pMapper->SetInput(pUnsGrid);
      vecActors[t] = pActor;
}

// Using vecActors to display all the tetrahedrons with different colors
each!

I have to find another way to enable different colors for each tetrahedron
because its very importent to this application. The colors have to
visualize the mesh's temperatures of a drilling simulation demo.

Thanks for reading my problem, I am looking forward for some ideas how to
solve this problem!

Cheers,

Paul Bütow


-----------------------------------------------------------------
Paul C. Buetow
Fraunhofer Institut für
Produktionstechnologie IPT
Virtual Reality Labor
Steinbachstraße 17
52074 Aachen

E-Mail: paul.buetow at ipt.fraunhofer.de
Internet: www.ipt.fraunhofer.de