From f9609fc87405a5dc193f766a83d7999a2190a817 Mon Sep 17 00:00:00 2001
From: Alexander Grayver <agrayver@erdw.ethz.ch>
Date: Wed, 31 Mar 2021 13:39:29 +0200
Subject: [PATCH] Add query methods for vtk cell types in ReferenceCell

---
 include/deal.II/grid/reference_cell.h |  21 +++++
 source/grid/reference_cell.cc         | 126 ++++++++++++++++++++++++++
 2 files changed, 147 insertions(+)

diff --git a/include/deal.II/grid/reference_cell.h b/include/deal.II/grid/reference_cell.h
index 0c45adc3be..cddd2d0e98 100644
--- a/include/deal.II/grid/reference_cell.h
+++ b/include/deal.II/grid/reference_cell.h
@@ -58,6 +58,7 @@ namespace internal
      */
     DEAL_II_CONSTEXPR dealii::ReferenceCell
                       make_reference_cell_from_int(const std::uint8_t kind);
+
   } // namespace ReferenceCell
 } // namespace internal
 
@@ -467,6 +468,26 @@ public:
   unsigned int
   exodusii_face_to_deal_face(const unsigned int face_n) const;
 
+  /**
+   * Return a VTK linear shape constant that corresponds to the reference cell.
+   */
+  unsigned int
+  vtk_linear_type() const;
+
+  /**
+   * Return a VTK quadratic shape constant that corresponds to the reference
+   * cell.
+   */
+  unsigned int
+  vtk_quadratic_type() const;
+
+  /**
+   * Return a VTK Lagrange shape constant that corresponds to the reference
+   * cell.
+   */
+  unsigned int
+  vtk_lagrange_type() const;
+
   /**
    * @}
    */
diff --git a/source/grid/reference_cell.cc b/source/grid/reference_cell.cc
index 9bafdb90a2..3acc0987d7 100644
--- a/source/grid/reference_cell.cc
+++ b/source/grid/reference_cell.cc
@@ -34,6 +34,47 @@
 
 DEAL_II_NAMESPACE_OPEN
 
+namespace
+{
+  namespace VTKCellType
+  {
+    // Define VTK constants for linear, quadratic and
+    // high-order Lagrange geometrices
+    enum
+    {
+      VTK_VERTEX = 1,
+      // Linear cells
+      VTK_LINE       = 3,
+      VTK_TRIANGLE   = 5,
+      VTK_QUAD       = 9,
+      VTK_TETRA      = 10,
+      VTK_HEXAHEDRON = 12,
+      VTK_WEDGE      = 13,
+      VTK_PYRAMID    = 14,
+      // Quadratic cells
+      VTK_QUADRATIC_EDGE       = 21,
+      VTK_QUADRATIC_TRIANGLE   = 22,
+      VTK_QUADRATIC_QUAD       = 23,
+      VTK_QUADRATIC_TETRA      = 24,
+      VTK_QUADRATIC_HEXAHEDRON = 25,
+      VTK_QUADRATIC_WEDGE      = 26,
+      VTK_QUADRATIC_PYRAMID    = 27,
+      // Lagrange cells
+      VTK_LAGRANGE_CURVE         = 68,
+      VTK_LAGRANGE_TRIANGLE      = 69,
+      VTK_LAGRANGE_QUADRILATERAL = 70,
+      VTK_LAGRANGE_TETRAHEDRON   = 71,
+      VTK_LAGRANGE_HEXAHEDRON    = 72,
+      VTK_LAGRANGE_WEDGE         = 73,
+      VTK_LAGRANGE_PYRAMID       = 74,
+      // Invalid code
+      VTK_INVALID = static_cast<unsigned int>(-1)
+    };
+
+  } // namespace VTKCellType
+
+} // namespace
+
 
 std::string
 ReferenceCell::to_string() const
@@ -292,6 +333,91 @@ ReferenceCell::exodusii_face_to_deal_face(const unsigned int face_n) const
 
 
 
+unsigned int
+ReferenceCell::vtk_linear_type() const
+{
+  if (*this == ReferenceCells::Vertex)
+    return VTKCellType::VTK_VERTEX;
+  else if (*this == ReferenceCells::Line)
+    return VTKCellType::VTK_LINE;
+  else if (*this == ReferenceCells::Triangle)
+    return VTKCellType::VTK_TRIANGLE;
+  else if (*this == ReferenceCells::Quadrilateral)
+    return VTKCellType::VTK_QUAD;
+  else if (*this == ReferenceCells::Tetrahedron)
+    return VTKCellType::VTK_TETRA;
+  else if (*this == ReferenceCells::Pyramid)
+    return VTKCellType::VTK_PYRAMID;
+  else if (*this == ReferenceCells::Wedge)
+    return VTKCellType::VTK_WEDGE;
+  else if (*this == ReferenceCells::Hexahedron)
+    return VTKCellType::VTK_HEXAHEDRON;
+  else if (*this == ReferenceCells::Invalid)
+    return VTKCellType::VTK_INVALID;
+
+  Assert(false, ExcNotImplemented());
+
+  return VTKCellType::VTK_INVALID;
+}
+
+
+
+unsigned int
+ReferenceCell::vtk_quadratic_type() const
+{
+  if (*this == ReferenceCells::Vertex)
+    return VTKCellType::VTK_VERTEX;
+  else if (*this == ReferenceCells::Line)
+    return VTKCellType::VTK_QUADRATIC_EDGE;
+  else if (*this == ReferenceCells::Triangle)
+    return VTKCellType::VTK_QUADRATIC_TRIANGLE;
+  else if (*this == ReferenceCells::Quadrilateral)
+    return VTKCellType::VTK_QUADRATIC_QUAD;
+  else if (*this == ReferenceCells::Tetrahedron)
+    return VTKCellType::VTK_QUADRATIC_TETRA;
+  else if (*this == ReferenceCells::Pyramid)
+    return VTKCellType::VTK_QUADRATIC_PYRAMID;
+  else if (*this == ReferenceCells::Wedge)
+    return VTKCellType::VTK_QUADRATIC_WEDGE;
+  else if (*this == ReferenceCells::Hexahedron)
+    return VTKCellType::VTK_QUADRATIC_HEXAHEDRON;
+  else if (*this == ReferenceCells::Invalid)
+    return VTKCellType::VTK_INVALID;
+
+  Assert(false, ExcNotImplemented());
+
+  return VTKCellType::VTK_INVALID;
+}
+
+
+
+unsigned int
+ReferenceCell::vtk_lagrange_type() const
+{
+  if (*this == ReferenceCells::Vertex)
+    return VTKCellType::VTK_VERTEX;
+  else if (*this == ReferenceCells::Line)
+    return VTKCellType::VTK_LAGRANGE_CURVE;
+  else if (*this == ReferenceCells::Triangle)
+    return VTKCellType::VTK_LAGRANGE_TRIANGLE;
+  else if (*this == ReferenceCells::Quadrilateral)
+    return VTKCellType::VTK_LAGRANGE_QUADRILATERAL;
+  else if (*this == ReferenceCells::Tetrahedron)
+    return VTKCellType::VTK_LAGRANGE_TETRAHEDRON;
+  else if (*this == ReferenceCells::Pyramid)
+    return VTKCellType::VTK_LAGRANGE_PYRAMID;
+  else if (*this == ReferenceCells::Wedge)
+    return VTKCellType::VTK_LAGRANGE_WEDGE;
+  else if (*this == ReferenceCells::Hexahedron)
+    return VTKCellType::VTK_LAGRANGE_HEXAHEDRON;
+  else if (*this == ReferenceCells::Invalid)
+    return VTKCellType::VTK_INVALID;
+
+  Assert(false, ExcNotImplemented());
+
+  return VTKCellType::VTK_INVALID;
+}
+
 #include "reference_cell.inst"
 
 DEAL_II_NAMESPACE_CLOSE
-- 
2.39.5