mirror of https://github.com/CGAL/cgal
Fix edge collapse with incident non-triangular faces (#9117)
Make collapse able to handle non-triangular faces. The fix is easy as you simply don't need to join faces in case the face won't disappear after collapse **TODO:** update doc and constrained version
This commit is contained in:
Sebastien Loriot
GitHub
commit
dee5ed8cc2
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@ -1543,10 +1543,10 @@ does_satisfy_link_condition(typename boost::graph_traits<Graph>::edge_descriptor
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*
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* After the collapse of edge `e` the following holds:
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* - The edge `e` is no longer in `g`.
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* - The faces incident to edge `e` are no longer in `g`.
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* - The triangle faces incident to edge `e` are no longer in `g`.
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* - `v0` is no longer in `g`.
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* - If `h` is not a border halfedge, `p_h` is no longer in `g` and is replaced by `o_n_h`.
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* - If the opposite of `h` is not a border halfedge, `p_o_h` is no longer in `g` and is replaced by `o_n_o_h`.
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* - If `h` is part of a triangle face, `p_h` is no longer in `g` and is replaced by `o_n_h`.
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* - If the opposite of `h` is part of a triangle face, `p_o_h` is no longer in `g` and is replaced by `o_n_o_h`.
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* - The halfedges kept in `g` that had `v0` as target and source now have `v1` as target and source, respectively.
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* - No other incidence information is changed in `g`.
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*
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@ -1575,9 +1575,8 @@ collapse_edge(typename boost::graph_traits<Graph>::edge_descriptor e,
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bool lBottomFaceExists = ! is_border(qp,g);
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bool lTopLeftFaceExists = lTopFaceExists && ! is_border(pt,g);
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bool lBottomRightFaceExists = lBottomFaceExists && ! is_border(qb,g);
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CGAL_precondition( !lTopFaceExists || (lTopFaceExists && ( degree(target(pt, g), g) > 2 ) ) ) ;
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CGAL_precondition( !lBottomFaceExists || (lBottomFaceExists && ( degree(target(qb, g), g) > 2 ) ) ) ;
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bool lBottomIsTriangle = lBottomFaceExists && is_triangle(qp,g);
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bool lTopIsTriangle = lTopFaceExists && is_triangle(pq,g);
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vertex_descriptor q = target(pq, g);
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vertex_descriptor p = source(pq, g);
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@ -1585,7 +1584,7 @@ collapse_edge(typename boost::graph_traits<Graph>::edge_descriptor e,
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bool lP_Erased = false;
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if ( lTopFaceExists )
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if ( lTopIsTriangle)
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{
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CGAL_precondition( ! is_border(opposite(pt, g),g) ) ; // p-q-t is a face of the mesh
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if ( lTopLeftFaceExists )
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@ -1612,7 +1611,7 @@ collapse_edge(typename boost::graph_traits<Graph>::edge_descriptor e,
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}
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}
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if ( lBottomFaceExists )
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if ( lBottomIsTriangle)
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{
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CGAL_precondition( ! is_border(opposite(qb, g),g) ) ; // p-q-b is a face of the mesh
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if ( lBottomRightFaceExists )
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@ -1659,7 +1658,7 @@ collapse_edge(typename boost::graph_traits<Graph>::edge_descriptor e,
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* collapses an edge in a graph having non-collapsable edges.
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*
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* Let `h` be the halfedge of `e`, and let `v0` and `v1` be the source and target vertices of `h`.
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* Collapses the edge `e` replacing it with `v1`, as described in the paragraph above
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* Collapses the edge `e` replacing it with `v1`, as described in the other overload
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* and guarantees that an edge `e2`, for which `get(edge_is_constrained_map, e2)==true`,
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* is not removed after the collapse.
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*
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@ -1669,14 +1668,14 @@ collapse_edge(typename boost::graph_traits<Graph>::edge_descriptor e,
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*
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* \returns vertex `v1`.
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* \pre This function requires `g` to be an oriented 2-manifold with or without boundaries.
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* Furthermore, the edge `v0v1` must satisfy the link condition, which guarantees that the surface mesh is also 2-manifold after the edge collapse.
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* \pre `get(edge_is_constrained_map, v0v1)==false`.
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* Furthermore, the edge `e` must satisfy the link condition, which guarantees that the surface mesh is also 2-manifold after the edge collapse.
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* \pre `get(edge_is_constrained_map, e)==false`.
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* \pre `v0` and `v1` are not both incident to a constrained edge.
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*/
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template<typename Graph, typename EdgeIsConstrainedMap>
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typename boost::graph_traits<Graph>::vertex_descriptor
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collapse_edge(typename boost::graph_traits<Graph>::edge_descriptor v0v1,
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collapse_edge(typename boost::graph_traits<Graph>::edge_descriptor e,
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Graph& g,
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EdgeIsConstrainedMap Edge_is_constrained_map)
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{
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@ -1684,11 +1683,11 @@ collapse_edge(typename boost::graph_traits<Graph>::edge_descriptor v0v1,
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typedef typename Traits::vertex_descriptor vertex_descriptor;
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typedef typename Traits::halfedge_descriptor halfedge_descriptor;
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CGAL_precondition(is_valid_edge_descriptor(v0v1, g));
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CGAL_precondition(does_satisfy_link_condition(v0v1,g));
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CGAL_precondition(!get(Edge_is_constrained_map, v0v1));
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CGAL_precondition(is_valid_edge_descriptor(e, g));
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CGAL_precondition(does_satisfy_link_condition(e,g));
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CGAL_precondition(!get(Edge_is_constrained_map, e));
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halfedge_descriptor pq = halfedge(v0v1,g);
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halfedge_descriptor pq = halfedge(e,g);
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halfedge_descriptor qp = opposite(pq,g);
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halfedge_descriptor pt = opposite(prev(pq,g),g);
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@ -1698,6 +1697,8 @@ collapse_edge(typename boost::graph_traits<Graph>::edge_descriptor v0v1,
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bool lTopFaceExists = ! is_border(pq,g) ;
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bool lBottomFaceExists = ! is_border(qp,g) ;
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bool lTopIsTriangle = lTopFaceExists && is_triangle(pq,g);
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bool lBottomIsTriangle = lBottomFaceExists && is_triangle(qp,g);
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vertex_descriptor q = target(pq,g);
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vertex_descriptor p = source(pq,g);
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@ -1708,7 +1709,7 @@ collapse_edge(typename boost::graph_traits<Graph>::edge_descriptor v0v1,
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// If the top facet exists, we need to choose one out of the two edges which one disappears:
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// p-t if it is not constrained and t-q otherwise
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if ( lTopFaceExists )
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if ( lTopIsTriangle )
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{
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if ( !get(Edge_is_constrained_map,edge(pt,g)) )
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{
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@ -1722,7 +1723,7 @@ collapse_edge(typename boost::graph_traits<Graph>::edge_descriptor v0v1,
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// If the bottom facet exists, we need to choose one out of the two edges which one disappears:
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// q-b if it is not constrained and b-p otherwise
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if ( lBottomFaceExists )
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if ( lBottomIsTriangle )
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{
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if ( !get(Edge_is_constrained_map,edge(qb,g)) )
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{
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@ -1733,7 +1734,7 @@ collapse_edge(typename boost::graph_traits<Graph>::edge_descriptor v0v1,
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}
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}
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if (lTopFaceExists && lBottomFaceExists)
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if (lTopIsTriangle && lBottomIsTriangle)
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{
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if ( face(edges_to_erase[0],g) == face(edges_to_erase[1],g)
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&& (! is_border(edges_to_erase[0],g)) )
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@ -1780,7 +1781,7 @@ collapse_edge(typename boost::graph_traits<Graph>::edge_descriptor v0v1,
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}
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else
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{
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if (lTopFaceExists)
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if (lTopIsTriangle)
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{
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if (!(is_border(edges_to_erase[0],g))){
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join_face(edges_to_erase[0],g);
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@ -1795,21 +1796,32 @@ collapse_edge(typename boost::graph_traits<Graph>::edge_descriptor v0v1,
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remove_face(opposite(edges_to_erase[0],g),g);
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return q;
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}
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if (! (is_border(edges_to_erase[0],g))){
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// q will be removed, swap it with p
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internal::swap_vertices(p, q, g);
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join_face(edges_to_erase[0],g);
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join_vertex(qp,g);
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return q;
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}
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if(!is_border(opposite(next(qp,g),g),g))
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else
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{
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// q will be removed, swap it with p
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internal::swap_vertices(p, q, g);
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if (lBottomIsTriangle)
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{
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if (! (is_border(edges_to_erase[0],g))){
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// q will be removed, swap it with p
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internal::swap_vertices(p, q, g);
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join_face(edges_to_erase[0],g);
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CGAL_assertion(source(qp,g)==p);
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join_vertex(qp,g);
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return q;
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}
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if(!is_border(opposite(next(qp,g),g),g))
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{
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// q will be removed, swap it with p
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internal::swap_vertices(p, q, g);
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}
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remove_face(opposite(edges_to_erase[0],g),g);
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return q;
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}
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else
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{
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join_vertex(pq,g);
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return q;
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}
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}
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remove_face(opposite(edges_to_erase[0],g),g);
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return q;
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}
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}
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@ -0,0 +1,42 @@
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OFF
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25 13 0
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0.39160239696502686 1.3864846229553223 4.8046874923102223e-08
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0.053782559931278229 1.3864846229553223 4.8046874923102223e-08
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-0.94644606113433838 1.6651756763458252 4.8046874923102223e-08
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-1.3082554340362549 1.7385153770446777 4.8046874923102223e-08
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-1.3033660650253296 1.1860226392745972 4.8046874923102223e-08
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1.61628258228302 -0.17601536214351654 4.8046874923102223e-08
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0.55834579467773438 -0.19216139614582062 4.8046874923102223e-08
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0.053782559931278229 -0.17601536214351654 4.8046874923102223e-08
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-0.24240998923778534 -0.22679123282432556 4.8046874923102223e-08
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-0.58168435096740723 -0.25845989584922791 4.8046874923102223e-08
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-1.2915089130401611 -0.17601536214351654 4.8046874923102223e-08
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-1.50871741771698 -0.17601536214351654 4.8046874923102223e-08
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1.61628258228302 -1.7385153770446777 4.8046874923102223e-08
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1.1978726387023926 -1.7385153770446777 4.8046874923102223e-08
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0.71942150592803955 -1.7385153770446777 4.8046874923102223e-08
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0.053782559931278229 -1.7385153770446777 4.8046874923102223e-08
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-0.73973840475082397 -1.7385153770446777 4.8046874923102223e-08
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1.61628258228302 0.36264327168464661 4.8046874923102223e-08
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-0.26156377792358398 0.45463424921035767 4.8046874923102223e-08
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-0.028661971911787987 -0.78840988874435425 4.8046874923102223e-08
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0.053782559931278229 -1.2213115692138672 4.8046874923102223e-08
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-1.5918357372283936 1.5331641435623169 4.8046874923102223e-08
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-1.6162823438644409 0.87338578701019287 4.8046874923102223e-08
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-1.50871741771698 -0.0072435899637639523 4.8046874923102223e-08
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-1.50871741771698 -1.3000825643539429 4.8046874923102223e-08
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7 18 2 3 4 22 9 8
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3 2 18 1
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7 18 7 6 5 17 0 1
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7 12 5 6 7 8 19 13
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6 11 24 16 15 20 10
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3 9 19 8
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4 10 20 19 9
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3 7 18 8
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3 14 20 15
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4 13 19 20 14
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3 3 21 4
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4 9 22 23 10
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3 10 23 11
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@ -2,7 +2,6 @@
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#include <CGAL/boost/graph/Euler_operations.h>
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#include <CGAL/boost/graph/IO/OFF.h>
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#include <boost/range/distance.hpp>
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#include <string>
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@ -213,12 +212,30 @@ collapse_edge_test()
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assert(found == 2);
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CGAL::clear(test_mesh);
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}
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// Case 6 non pure triangle mesh
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{
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Mesh ref;
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if(!CGAL::IO::read_OFF("data/polygon_mesh_to_collapse.off", ref))
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{
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std::cout << "Error reading file: data/polygon_mesh_to_collapse.off" << std::endl;
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exit(1);
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}
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std::size_t nbe=halfedges(ref).size();
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for (std::size_t i=0; i< nbe; ++i)
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{
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Mesh m = ref;
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auto h = *std::next(halfedges(m).begin(), i);
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if (CGAL::Euler::does_satisfy_link_condition(edge(h,m),m))
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CGAL::Euler::collapse_edge(edge(h,m), m);
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assert(CGAL::is_valid_polygon_mesh(m));
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}
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}
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}
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int main()
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{
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collapse_edge_test<Polyhedron>();
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collapse_edge_test<SM>();
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