mesh_conversion.h

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#pragma once
 
#include <pcl/PolygonMesh.h>
#include <pcl/conversions.h>
 
namespace pcl
{
  namespace geometry
  {
    /** \brief Convert a half-edge mesh to a face-vertex mesh.
      * \param[in] half_edge_mesh The input mesh.
      * \param[out] face_vertex_mesh The output mesh.
      * \author Martin Saelzle
      * \ingroup geometry
      */
    template <class HalfEdgeMeshT> void
    toFaceVertexMesh (const HalfEdgeMeshT& half_edge_mesh, pcl::PolygonMesh& face_vertex_mesh)
    {
      using HalfEdgeMesh = HalfEdgeMeshT;
      using VAFC = typename HalfEdgeMesh::VertexAroundFaceCirculator;
      using FaceIndex = typename HalfEdgeMesh::FaceIndex;
 
      pcl::Vertices polygon;
      pcl::toPCLPointCloud2 (half_edge_mesh.getVertexDataCloud (), face_vertex_mesh.cloud);
 
      face_vertex_mesh.polygons.reserve (half_edge_mesh.sizeFaces ());
      for (std::size_t i=0; i<half_edge_mesh.sizeFaces (); ++i)
      {
        VAFC       circ     = half_edge_mesh.getVertexAroundFaceCirculator (FaceIndex (i));
        const VAFC circ_end = circ;
        polygon.vertices.clear ();
        do
        {
          polygon.vertices.push_back (circ.getTargetIndex ().get ());
        } while (++circ != circ_end);
        face_vertex_mesh.polygons.push_back (polygon);
      }
    }
 
    /** \brief Convert a face-vertex mesh to a half-edge mesh.
      * \param[in] face_vertex_mesh The input mesh.
      * \param[out] half_edge_mesh The output mesh. It must have data associated with the vertices.
      * \return The number of faces that could NOT be added to the half-edge mesh.
      * \author Martin Saelzle
      * \ingroup geometry
      */
    template <class HalfEdgeMeshT> int
    toHalfEdgeMesh (const pcl::PolygonMesh& face_vertex_mesh, HalfEdgeMeshT& half_edge_mesh)
    {
      using HalfEdgeMesh = HalfEdgeMeshT;
      using VertexDataCloud = typename HalfEdgeMesh::VertexDataCloud;
      using VertexIndices = typename HalfEdgeMesh::VertexIndices;
 
      static_assert (HalfEdgeMesh::HasVertexData::value, "Output mesh must have data associated with the vertices!");
 
      VertexDataCloud vertices;
      pcl::fromPCLPointCloud2 (face_vertex_mesh.cloud, vertices);
 
      half_edge_mesh.reserveVertices (vertices.size ());
      half_edge_mesh.reserveEdges (3 * face_vertex_mesh.polygons.size ());
      half_edge_mesh.reserveFaces (    face_vertex_mesh.polygons.size ());
 
      for (const auto &vertex : vertices)
      {
        half_edge_mesh.addVertex (vertex);
      }
 
      assert (half_edge_mesh.sizeVertices () == vertices.size ());
 
      int count_not_added = 0;
      VertexIndices vi;
      vi.reserve (3); // Minimum number (triangle)
      for (const auto &polygon : face_vertex_mesh.polygons)
      {
        vi.clear ();
        for (const auto &vertex : polygon.vertices)
        {
          vi.emplace_back (vertex);
        }
 
        if (!half_edge_mesh.addFace (vi).isValid ())
        {
          ++count_not_added;
        }
      }
 
      return (count_not_added);
    }
  } // End namespace geometry
} // End namespace pcl