VTK/Polyhedron Support

Goals:

• Add support for arbitrary polyhedral cell (manifold, watertight, may be concave)
• Develop smooth interpolation functions for polyhedron
• Create filters, examples and testing infrastructure supporting this technology
• Application goal: support CFD solvers (finite volume methods for computational fluid dynamics and similar)

Summary of Implementation Plan:

• Identify interpolation functions
  • Mean Value Coordinates
  • Triangle meshes (paper by Tao Ju et al.)
  • Arbitrary polyhedron (paper by Torsten Langer et al.)
• Polyhedron cell support
  • vtkPolyhedron - more complex cell in that it requires explicit face representation
  • vtkUnstructuredGrid - modified to support polyhedron cell, new InsertNextCell() and related methods (e.g., GetFace()).
  • vtkGenericCell expanded to include vtkPolyhedron
  • vtkCellTypes.h has new #define VTK_POLYHEDRON
• Implement cool related interpolation functions & filters
  • vtkMeanValueCoordinatesInterpolator
  • vtkProbePolyhedron - probe the region (interior, surface, exterior) around a polyhedral mesh for data values.
  • vtkDeformPointSet - use MVC to deform any vtkPointSet using control mesh
  • vtkExtractPolyhedralMesh - for debugging, convert 3D cells to vtkPolyhedron
  • Would like to implement some VTK widgets to manipulate meshes
    • vtkPancakeWidget (local surface deformation)
    • vtkControlMeshWidget (for global deformation of geometry)

Implementation Issues:

• VTK File formats and IO
  • XML formats
  • Legacy formats
• Critical filters /functionality
  • Geometry Filter - should work once vtkCell::GetCellNeighbors() is implemented
  • Contouring - some work required
  • Clipping - serious work required
  • Search (vtkDataSet::FindCell() and FindPoint()) - should work once evaluation functions are implemented
• Impact on previous code
  • Previous vtkClipDataSet can now produce polyhedron as output, is this desirable?

Auxiliary Tasks

• vtkPolygon basis functions: replace silly 1/r^2 with the MVC 2D equivalent

Contacts:

• Will Schroeder (will.schroeder at kitware.com)
• Hua Yang (hua.yang at kitware.com)