I was wondering if anyone has some good ideas as to a fast
way to find the intersection between a triangular surface and a plane
which goes through it?

Daphne,

Make your triangle PolyData (you can use UnstructuredGrid) and then just create a slice plane. Then you will get a line as the output polydata from the slicer.

The UGrid.cxx example in vtk/graphics.cxx shows how to do the UnstructuredGrid using VTK_TRIANGLE.

Heres how to slice (this is for a horizontal slice, for arbitrary dip just set the normal to the plane and the rotation point differently):
      

// This you build as in the UGrid.cxx example
      vtkUnstructuredGrid *uGrid;

      float slicePoint[3],sliceNormal[3];

      slicePoint[0] = X;
      slicePoint[1] = Y;
      slicePoint[2] = Z;

      sliceNormal[0] = 0.0f;
      sliceNormal[1] = 0.0f;
      sliceNormal[2] = 1.0f;

      vtkPlane *slicePlane = vtkPlane::New();
        slicePlane->SetOrigin(slicePoint);
        slicePlane->SetNormal(sliceNormal);

      vtkCutter *cut = vtkCutter::New();
        cut->SetInput(uGrid);
        cut->SetCutFunction (slicePlane);

regards,

john Attachment Converted: "c:\program files\qualcomm\eudora mail\attach\washbourne11.vcf"