Function BuildFaceAdjacency

src/colmap/mvs/texture_mapping.cc:155–183

}

FaceAdjacencyMap BuildFaceAdjacency(const PlyMesh& mesh) {
  const size_t num_faces = mesh.faces.size();
  std::unordered_map<uint64_t, std::vector<size_t>> edge_to_faces;
  edge_to_faces.reserve(num_faces * 3);

  for (size_t fi = 0; fi < num_faces; ++fi) {
    const std::array<size_t, 3> idx = GetFaceIndices(mesh.faces[fi]);
    for (int e = 0; e < 3; ++e) {
      const uint64_t key = EdgeKey(idx[e], idx[(e + 1) % 3]);
      edge_to_faces[key].push_back(fi);
    }
  }

  FaceAdjacencyMap adjacency(num_faces);
  for (const auto& [edge_key, face_list] : edge_to_faces) {
    if (face_list.size() == 2) {
      adjacency[face_list[0]].push_back(face_list[1]);
      adjacency[face_list[1]].push_back(face_list[0]);
    }
  }

  for (auto& neighbors : adjacency) {
    std::sort(neighbors.begin(), neighbors.end());
    neighbors.erase(std::unique(neighbors.begin(), neighbors.end()),
                    neighbors.end());
  }

  return adjacency;
}

#if defined(COLMAP_CGAL_ENABLED)