# VTK/Polyhedron Support

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**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
- 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 (and vtkUnstructuredGrid::GetCell() methods) expanded to include vtkPolyhedron
- vtkCellTypes.h has new #define VTK_POLYHEDRON

- Implement cool related interpolation functions & filters
*(note items in green are complete)*- 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

**Schedule**

- Working on core functionality which should be done by mid 2010. Completion of all work depends on funding, schedule and customer support.
- Basics- polygon2d, data API and integration, Mesh2Polyhedra filter, Evaluate/Location/Position functions() in vtkPolyhedron, GetCellNeighbors(), GetFace(), GetFaceIds() (Early March)
- Core- geometry filter, IO (mid-March)
- Algorithms- (clipping, contouring) (early to mid April)
- Final tuning (mid to late April)

**Contacts:**

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