c++ - 表面网格-去除边缘，循环进入无限循环CGAL

Question

我正在制作 slice 函数，该函数删除 y 长度处的部分网格。当我尝试删除网格的已移除面边缘时，问题开始出现，它进入无限循环。

哪里出了问题!

//removes edge - puts in infinite loop
BOOST_FOREACH(halfEdge_descriptor hed, halfedges_around_face(mesh.halfedge(fd), mesh)){
 edge_descriptor ed = mesh.edge(hed);
 mesh.remove_edge(ed);
}

当我遍历 halfedges 时，它会按预期进行迭代，但是当我尝试通过转换为

remove_edge(Edge_index ed)

进入无限循环。

任何人都可以解释为什么会这样，我该如何解决？

完整代码!

void Mesh::slice(SurfaceMesh &mesh,  double lengthToCut){
  typedef SurfaceMesh::Vertex_index vertex_descriptor;
  typedef SurfaceMesh::Face_index face_descriptor;
  typedef SurfaceMesh::Halfedge_index halfEdge_descriptor;
  typedef SurfaceMesh::Edge_index edge_descriptor;
  double y = findMaxY(mesh) - lengthToCut; // length of a mesh
  //;oops over faces
  BOOST_FOREACH(face_descriptor fd, mesh.faces()){
    int verticesLargerThan = 0;
    //loops over vertices of face
    BOOST_FOREACH(vertex_descriptor vd,vertices_around_face(mesh.halfedge(fd), mesh)){
      if(CGAL::compare ( mesh.point(vd)[1],  y) == CGAL::LARGER){
        verticesLargerThan++;
        // if all vertices y coordinates are larger than double y, then removes face
        if(verticesLargerThan == 3){
          mesh.remove_face(fd);
          //mesh.remove_face(fd);
          int removedFaceCounter = 0;
          BOOST_FOREACH(face_descriptor rfd,faces_around_face(mesh.halfedge(fd), mesh)){
            if(mesh.is_removed(rfd)){
              removedFaceCounter++;
            }
            //remove all edges and vertices of face if face is not linked to any other face
            if(removedFaceCounter == 3){
              //removes edge - puts in infinite loop
              BOOST_FOREACH(halfEdge_descriptor hed, halfedges_around_face(mesh.halfedge(fd), mesh)){
                edge_descriptor ed = mesh.edge(hed);
                mesh.remove_edge(ed);
              }
              //removes vertice
              BOOST_FOREACH(vertex_descriptor rvd,vertices_around_face(mesh.halfedge(fd), mesh)){
                //removes vertice if its not linked to any face
                bool allFacesRemoved = true;
                BOOST_FOREACH(face_descriptor rfvd, faces_around_target(mesh.halfedge(fd), mesh)){

                  if(!mesh.is_removed(rfvd)){
                    allFacesRemoved = false;
                    break;
                  }
                }
                if(allFacesRemoved){
                  mesh.remove_vertex(rvd);
                }
              }
            }
          }
        }
      }
    }
  }

Answer 1

这是一个典型的错误:删除您正在迭代的元素。在这种特殊情况下，您将在迭代面部边缘的同时移除边缘。您不太可能会找到停止迭代的初始边，因此会出现无限循环。