[vtk-developers] New nonlinear celltypes

[Soeren Gebbert]

Dear developers,
sorry for the delay, i was on vacation for a while.
Thank you for your help!

Im still developing the nonlinear cells. Tcl test running well.
I have extendet the contouring, clipping and edge-extraction quadratic 
cell tcl tests.
The tcl errors i reported bevor are no erros, it was all my fault.

But i still runing into a problem im not able to fix. I have implemented 
contouring and
clipping of the new cells. The methods for that are quite similar. The 
contouring
is working very well, but the clipping produces strange output. I have 
attached some pictures of
the TriQuadraticHexahedron, to show you the point.

I have defined 8 linear hexes and contour and clip them. Contouring dont 
have any problems with that.
But "clipping by value" produce wired output.
The result changes if i change the index of linear hexes. I tried the exact
(internal) enumeration of vtkQuadraticHexahedron, but the result is 
still looking strange.
I tried some permutation, but never got a acceptable result.

Some pictures of the triquadratic Hexahedron:

Normal view with scalar labeling
http://www-pool.math.tu-berlin.de/~soeren/VTK/Pictures/TriQuadraticHexahedron.png

Edge View with scalar labeling
http://www-pool.math.tu-berlin.de/~soeren/VTK/Pictures/TriQuadraticHexahedron-edges.png

Contour (value 0.5) view with scalar labeling
http://www-pool.math.tu-berlin.de/~soeren/VTK/Pictures/TriQuadraticHexahedron-contour.png

Clipping (value 0.5) view with scalar labeling --< strange clipping
http://www-pool.math.tu-berlin.de/~soeren/VTK/Pictures/TriQuadraticHexahedron-clip-value.png

Tessellation view with scalar labeling
http://www-pool.math.tu-berlin.de/~soeren/VTK/Pictures/TriQuadraticHexahedron-tessellated.png

Is there a magic rule in enumeration of the linear hexes/Wedges to get 
this to work? I have these Problems
with 3 new Celltypes:
vtkTriQuadraticHexahedron
vtkBiQuadraticHexahedron
vtkBiquaraticQuadraticWedge

This is a code example from vtkTriQuadraticHexahedron:

//----------------------------------------------------------------------------
void
vtkTriQuadraticHexahedron::Contour (double value,
                    vtkDataArray * cellScalars,
                    vtkPointLocator * locator,
                    vtkCellArray * verts,
                    vtkCellArray * lines,
                    vtkCellArray * polys,
                    vtkPointData * inPd,
                    vtkPointData * outPd,
                    vtkCellData * inCd, vtkIdType cellId, vtkCellData * 
outCd)
{
  int i, j;

  //contour each linear quad separately
  for (i = 0; i < 8; i++)
    {
      for (j = 0; j < 8; j++)
    {
      this->Hex->Points->SetPoint (j, this->Points->GetPoint 
(LinearHexs[i][j]));
      this->Hex->PointIds->SetId (j, LinearHexs[i][j]);
      this->Scalars->SetValue (j, cellScalars->GetTuple1 
(LinearHexs[i][j]));
    }
      this->Hex->Contour (value, this->Scalars, locator, verts, lines, 
polys, inPd, outPd, inCd, cellId, outCd);
    }
}

//----------------------------------------------------------------------------
// Clip this triquadratic hex using scalar value provided. Like contouring,
// except that it cuts the hex to produce tetrahedra.
void
vtkTriQuadraticHexahedron::Clip (double value,
                 vtkDataArray * cellScalars,
                 vtkPointLocator * locator,
                 vtkCellArray * tets,
                 vtkPointData * inPd,
                 vtkPointData * outPd,
                 vtkCellData * inCd, vtkIdType cellId, vtkCellData * 
outCd, int insideOut)
{
  int i, j;

  //clip each linear quad separately
  for (i = 0; i < 8; i++)
    {
      for (j = 0; j < 8; j++)
    {
      this->Hex->Points->SetPoint (j, this->Points->GetPoint 
(LinearHexs[i][j]));
      this->Hex->PointIds->SetId (j, LinearHexs[i][j]);
      this->Scalars->SetValue (j, cellScalars->GetTuple1 
(LinearHexs[i][j]));
    }
      this->Hex->Clip (value, this->Scalars, locator, tets, inPd, outPd, 
inCd, cellId, outCd, insideOut);
    }
}

Any help is welcome, i stuck on this for 3 days now.
After i resolved this (hopefully) last problem, i will take care of the 
vtkEnSightWriter.  

Thanks and best regards
Soeren Gebbert