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#include <CGAL/Simple_cartesian.h>
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#include <CGAL/Polyhedron_3.h>
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#include <CGAL/IO/Polyhedron_iostream.h>
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// Adaptor for Polyhedron_3
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#include <CGAL/Surface_mesh_simplification/HalfedgeGraph_Polyhedron_3.h>
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// Simplification function
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#include <CGAL/Surface_mesh_simplification/edge_collapse.h>
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// Stop-condition policy
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#include <CGAL/Surface_mesh_simplification/Policies/Edge_collapse/Count_stop_predicate.h>
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// Map used to mark edges as fixed
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#include <CGAL/Unique_hash_map.h>
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typedef CGAL::Simple_cartesian<double> Kernel;
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typedef CGAL::Polyhedron_3<Kernel> Surface;
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namespace SMS = CGAL::Surface_mesh_simplification ;
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// BGL property map which indicates whether an edge is border OR is marked as non-removable
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class Constrains_map : public boost::put_get_helper<bool,Constrains_map>
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typedef boost::readable_property_map_tag category;
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typedef bool value_type;
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typedef bool reference;
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typedef boost::graph_traits<Surface const>::edge_descriptor key_type;
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Constrains_map() : mConstrains(false) {}
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reference operator[](key_type const& e) const { return e->is_border() || is_constrained(e) ; }
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void set_is_constrained ( key_type const& e, bool is ) { mConstrains[e]=is; }
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bool is_constrained( key_type const& e ) const { return mConstrains.is_defined(e) ? mConstrains[e] : false ; }
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CGAL::Unique_hash_map<key_type,bool> mConstrains ;
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int main( int argc, char** argv )
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std::ifstream is(argv[1]) ; is >> surface ;
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// This is a stop predicate (defines when the algorithm terminates).
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// In this example, the simplification stops when the number of undirected edges
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// left in the surface drops below the specified number (1000)
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SMS::Count_stop_predicate<Surface> stop(10);
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Constrains_map constrains_map ;
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// This example marks ALL edges as non-removable, but a real world application would mark only selected ones.
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for( Surface::Halfedge_iterator eb = surface.halfedges_begin(), ee = surface.halfedges_end() ; eb != ee ; ++ eb )
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constrains_map.set_is_constrained(eb,true);
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// This the actual call to the simplification algorithm.
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// The surface and stop conditions are mandatory arguments.
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// The index maps are needed because the vertices and edges
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// of this surface lack an "id()" field.
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int r = SMS::edge_collapse
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,CGAL::vertex_index_map(boost::get(CGAL::vertex_external_index,surface))
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.edge_index_map (boost::get(CGAL::edge_external_index ,surface))
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.edge_is_border_map(constrains_map)
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std::cout << "\nFinished...\n" << r << " edges removed.\n"
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<< (surface.size_of_halfedges()/2) << " final edges.\n" ;
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std::ofstream os( argc > 2 ? argv[2] : "out.off" ) ; os << surface ;
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examples/Surface_mesh_simplification/edge_collapse_constrained_polyhedron.cpp
