mesh_conversion.h

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#pragma once
 
#include <pcl/conversions.h>
#include <pcl/PolygonMesh.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