CGAL 4.12 - Triangulated Surface Mesh Shortest Paths
SurfaceMeshShortestPathVisitor Concept Reference

## Definition

The concept SurfaceMeshShortestPathVisitor describes the requirements of the visitor type used to collect the edges and vertices traversed by a shortest path on the surface of a triangulated surface mesh.

The methods are called in the order of the shortest path sequence along the surface, starting with the target point and ending with the source point.

## Methods

void operator() (halfedge_descriptor edge, FT alpha)
Called when an edge was traversed in the shortest path sequence. More...

void operator() (vertex_descriptor vertex)
Called when a vertex is encountered in the shortest path sequence. More...

void operator() (face_descriptor face, Barycentric_coordinates location)
Called when a face location is encountered in the shortest path sequence. More...

## ◆ operator()() [1/3]

 void SurfaceMeshShortestPathVisitor::operator() ( halfedge_descriptor edge, FT alpha )

Called when an edge was traversed in the shortest path sequence.

Parameters
 edge halfedge of the surface mesh crossed by the shortest path. The halfedge is directed toward the face nearest to the target point. alpha value in the range [0.0,1.0] specifying where along edge the shortest path crossed. 0.0 means it crossed at source(edge) 1.0 means it crossed at target(edge) Any other value is linearly interpolated between the endpoints.

Note that values of 0.0 and 1.0 are possible in some situations, and may not be reported as vertices. In particular, this will occur if the vertex crossed by the path is not a saddle vertex (less than $$2\pi$$ surface area). This is because from the perspective of the algorithm, this is indistinguishable from crossing anywhere else along the edge.

## ◆ operator()() [2/3]

 void SurfaceMeshShortestPathVisitor::operator() ( vertex_descriptor vertex )

Called when a vertex is encountered in the shortest path sequence.

Parameters
 vertex the vertex of the surface mesh encountered by the shortest path.

## ◆ operator()() [3/3]

 void SurfaceMeshShortestPathVisitor::operator() ( face_descriptor face, Barycentric_coordinates location )

Called when a face location is encountered in the shortest path sequence.

Remarks
This will only be called as the first and/or last element in the path sequence, and only if the target/source point is an internal face location (i.e. not on an edge or at a vertex).
Parameters
 face a face of the surface mesh encountered at the start or the end of the shortest path. location the barycentric coordinates inside face of this point on the path.