CGAL 5.1.3 - Triangulated Surface Mesh Simplification
EdgeCollapseSimplificationVisitor Concept Reference

## Definition

The concept EdgeCollapseSimplificationVisitor describes the requirements for the visitor object which is used to track the edge collapse simplification algorithm.

The several callbacks given as member functions in the visitor are called from certain places in the algorithm implementation.

## Types

typedef CGAL::Surface_mesh_simplification::Edge_profile Edge_profile
Convenience typedef to the Edge_profile class.

typedef Edge_profile::Triangle_mesh TriangleMesh
The type of the surface mesh to simplify. More...

## Operations

void OnStarted (TriangleMesh &surface_mesh)
Called before the algorithm starts.

void OnFinished (TriangleMesh &surface_mesh)
Called after the algorithm finishes.

void OnStopConditionReached (TriangleMesh &surface_mesh)
Called when the StopPredicate returned true (but not if the algorithm terminates because the surface mesh could not be simplified any further).

void OnCollected (const Edge_profile &profile, boost::optional< Edge_profile::FT > cost)
Called during the collecting phase (when a cost is assigned to the edges), for each edge collected.

void OnSelected (const Edge_profile &profile, boost::optional< Edge_profile::FT > cost, const Edge_profile::edges_size_type initial_edge_count, const Edge_profile::edges_size_type current_edge_count)
Called during the processing phase (when edges are collapsed), for each edge that is selected. More...

void OnCollapsing (const Edge_profile &profile, boost::optional< Edge_profile::Point > placement)
Called when an edge is about to be collapsed and replaced by a vertex whose position is *placement. More...

void OnCollapsed (const Edge_profile &profile, const Edge_profile::vertex_descriptor vd)
Called when an edge has been collapsed and replaced by the vertex vd

void OnNonCollapsable (const Edge_profile &profile)
Called for each selected edge which cannot be collapsed because doing so would change the topological type of the surface mesh (turn it into a non-manifold for instance).

## ◆ TriangleMesh

The type of the surface mesh to simplify.

Must be a model of the MutableFaceGraph and HalfedgeListGraph concepts.

## ◆ OnCollapsing()

 void EdgeCollapseSimplificationVisitor::OnCollapsing ( const Edge_profile & profile, boost::optional< Edge_profile::Point > placement )

Called when an edge is about to be collapsed and replaced by a vertex whose position is *placement.

If placement is absent (meaning that it could not be computed) the edge will not be collapsed.

## ◆ OnSelected()

 void EdgeCollapseSimplificationVisitor::OnSelected ( const Edge_profile & profile, boost::optional< Edge_profile::FT > cost, const Edge_profile::edges_size_type initial_edge_count, const Edge_profile::edges_size_type current_edge_count )

Called during the processing phase (when edges are collapsed), for each edge that is selected.

This method is called before the algorithm checks if the edge is collapsable.

cost indicates the current collapse cost for the edge. If absent (meaning that it could not be computed) the edge will not be collapsed.

initial_edge_count and current_edge_count refer to the number of edges.