Add CellTraits class

Currently it is pretty empty. It might make sense to roll this into the
CellShapeTag, but we may add more information later.

vtkm/CMakeLists.txt

@@ -24,6 +24,7 @@ set(headers
   BinaryPredicates.h
   BinaryOperators.h
   CellShape.h
+  CellTraits.h
   Extent.h
   ListTag.h
   Math.h

vtkm/CellShape.h

@@ -55,8 +55,10 @@ enum CellShapeIdEnum
 };
 
 // If you wish to add cell shapes to this list, in addition to adding an index
-// to the enum above, you need to define an associated tag with
+// to the enum above, you at a minimum need to define an associated tag with
 // VTKM_DEFINE_CELL_TAG and add a condition to the vtkmGenericCellShapeMacro.
+// There are also many other cell-specific features that code might expect such
+// as \c CellTraits and interpolations.
 
 namespace internal {
 

vtkm/CellTraits.h

@@ -0,0 +1,93 @@
+//============================================================================
+//  Copyright (c) Kitware, Inc.
+//  All rights reserved.
+//  See LICENSE.txt for details.
+//  This software is distributed WITHOUT ANY WARRANTY; without even
+//  the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+//  PURPOSE.  See the above copyright notice for more information.
+//
+//  Copyright 2014 Sandia Corporation.
+//  Copyright 2014 UT-Battelle, LLC.
+//  Copyright 2014 Los Alamos National Security.
+//
+//  Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation,
+//  the U.S. Government retains certain rights in this software.
+//
+//  Under the terms of Contract DE-AC52-06NA25396 with Los Alamos National
+//  Laboratory (LANL), the U.S. Government retains certain rights in
+//  this software.
+//============================================================================
+#ifndef vtk_m_CellTraits_h
+#define vtk_m_CellTraits_h
+
+#include <vtkm/CellShape.h>
+
+namespace vtkm {
+
+/// \c vtkm::CellTraits::TopologyDimensionType is typedef to this with the
+/// template parameter set to \c TOPOLOGICAL_DIMENSIONS. See \c
+/// vtkm::CellTraits for more information.
+///
+template<vtkm::IdComponent dimension>
+struct CellTopologicalDimensionsTag { };
+
+/// \brief Information about a cell based on its tag.
+///
+/// The templated CellTraits struct provides the basic high level information
+/// about cells (like the number of vertices in the cell or its
+/// dimensionality).
+///
+template<class CellTag>
+struct CellTraits
+#ifdef VTKM_DOXYGEN_ONLY
+{
+  /// This defines the topological dimensions of the cell type. 3 for
+  /// polyhedra, 2 for polygons, 1 for lines, 0 for points.
+  ///
+  const static vtkm::IdComponent TOPOLOGICAL_DIMENSIONS = 3;
+
+  /// This tag is typedef'ed to
+  /// vtkm::CellTopologicalDimensionsTag<TOPOLOGICAL_DIMENSIONS>. This provides
+  /// a convenient way to overload a function based on topological dimensions
+  /// (which is usually more efficient than conditionals).
+  ///
+  typedef vtkm::CellTopologicalDimensionsTag<TOPOLOGICAL_DIMENSIONS>
+      TopologicalDimensionsTag;
+};
+#else // VTKM_DOXYGEN_ONLY
+    ;
+#endif // VTKM_DOXYGEN_ONLY
+
+//-----------------------------------------------------------------------------
+
+// Define traits for every cell type.
+
+#define VTKM_DEFINE_CELL_TRAITS(name, dimensions) \
+  template<> \
+  struct CellTraits<vtkm::CellShapeTag ## name> { \
+    const static vtkm::IdComponent TOPOLOGICAL_DIMENSIONS = dimensions; \
+    typedef vtkm::CellTopologicalDimensionsTag<TOPOLOGICAL_DIMENSIONS> \
+        TopologicalDimensionsTag; \
+  }
+
+VTKM_DEFINE_CELL_TRAITS(Empty, 0);
+VTKM_DEFINE_CELL_TRAITS(Vertex, 0);
+//VTKM_DEFINE_CELL_TRAITS(PolyVertex, 0);
+VTKM_DEFINE_CELL_TRAITS(Line, 1);
+//VTKM_DEFINE_CELL_TRAITS(PolyLine, 1);
+VTKM_DEFINE_CELL_TRAITS(Triangle, 2);
+//VTKM_DEFINE_CELL_TRAITS(TriangleStrip, 2);
+VTKM_DEFINE_CELL_TRAITS(Polygon, 2);
+VTKM_DEFINE_CELL_TRAITS(Pixel, 2);
+VTKM_DEFINE_CELL_TRAITS(Quad, 2);
+VTKM_DEFINE_CELL_TRAITS(Tetra, 3);
+VTKM_DEFINE_CELL_TRAITS(Voxel, 3);
+VTKM_DEFINE_CELL_TRAITS(Hexahedron, 3);
+VTKM_DEFINE_CELL_TRAITS(Wedge, 3);
+VTKM_DEFINE_CELL_TRAITS(Pyramid, 3);
+
+#undef VTKM_DEFINE_CELL_TRAITS
+
+} // namespace vtkm
+
+#endif //vtk_m_CellTraits_h