[vtkusers] Clipping Planes

[James Robinson]

Dear All,

 

I am having trouble (again) with clipping planes. I am trying to create a
viewer to view results of an FE analysis. Part of the results are the
displacements at the nodes of the finite element mesh. I read in the FE mesh
into a vtkUnstructuredGrid with the displacements as a vector field. I then
create a displaced geometry by adding them to the vtkUnstructuredGrid
geometry as follows:

 

void CSampleDoc::AddDisplacement(float factor)

{   vtkFloatArray *pDisplacement =
(vtkFloatArray*)this->pUnstructuredGrid->GetPointData()->GetVectors() ;

 

            vtkPoints* pNodalGeometry = this->pUnstructuredGrid->GetPoints()
;

 

            if (pDisplacement==NULL)

            { AfxMessageBox("No displacement set") ;

              return ;

            }

 

 

            float newcoords[3] ;

            float* x ;

            float* delta ;

 

            for (int i = 0; i < pNodalGeometry->GetNumberOfPoints(); i++)

            {  

               x = pNodalGeometry->GetPoint(i) ;

       delta = pDisplacement->GetTuple(i) ;

               for (int j = 0; j < 3; j++)

       { newcoords[j] = x[j] + factor*delta[j] ;

               }

       pNodalGeometry->SetPoint(i,newcoords) ;

            }

    this->pUnstructuredGrid->Update() ;

    this->pGeometry->SetInput(pUnstructuredGrid) ;

    this->pMeshMapper->SetInput(pGeometry->GetOutput());

    this->pMeshMapper->Update() ;

    this->pMeshActor->SetMapper(this->pMeshMapper) ;

}

 

This works (with some other quirky behaviour which I have circumvented). But
a problem that I am having difficulty with is that the clipping planes
remain as if the geometry hadn't been altered. Thus, as I rotate the object
(in trackball camera mode) the displaced object disappears. I have checked
the bounds of the viewable objects (using
Renderer->ComputeVisiblePropBounds(bounds) ;) and they are unaltered - thus
all the AutoClipping is thrown out of whack. It may very well be that (a) I
am doing things that are not meant to be catered for in vtk or (b) there is
a better (preferably simpler) way of achieving this effect. 

 

All suggestions gratefully welcomed.

 

Jim

 

James C Robinson, PhD, Chartered Engineer,

*     42 Rivergrove,

         Glanmire,

         Co. Cork,

         Eire

'     +353 21 4822028

         +353 87 2393010

6      +353 21 4822028

*    j.robinson at kepler-systems.com 

 

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