LOD_EdgeCollapser.h

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/*
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
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 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * The Original Code is Copyright (C) 2001-2002 by NaN Holding BV.
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 * ***** END GPL LICENSE BLOCK *****
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#ifndef NAN_INCLDUED_EgdeCollapser_h
#define NAN_INCLDUED_EgdeCollapser_h

// This is a helper class that collapses edges of a 2 - manifold mesh.

#include "LOD_MeshPrimitives.h"
#include "MEM_NonCopyable.h"
#include <vector>
#include <functional>

class LOD_ManMesh2;

class LOD_EdgeCollapser 
: public  MEM_NonCopyable
{

public :
            
    static
        LOD_EdgeCollapser * 
    New(
    );

    // returns via arguments the set of modified
    // verts,edges and faces.

        bool
    CollapseEdge(
        LOD_EdgeInd ei,
        LOD_ManMesh2 &mesh,
        std::vector<LOD_EdgeInd> &  degenerate_edges,
        std::vector<LOD_FaceInd> &  degenerate_faces,
        std::vector<LOD_VertexInd> & degenerate_vertices,
        std::vector<LOD_EdgeInd> &  new_edges,
        std::vector<LOD_FaceInd> &  update_faces,
        std::vector<LOD_VertexInd> & update_vertices
    );

private :

    LOD_EdgeCollapser(
    );

    // Test to see if the result of collapsing the
    // edge produces 2 junctions in the mesh i.e. where
    // an edge is shared by more than 2 polygons

    // We count the number of coincedent edge pairs that
    // result from the collapse of collapse_edge.

    // If collapse edge is a boundary edge then the number of
    // coincedent pairs should be 1
    // else it should be 2.

        bool
    TJunctionTest(
        LOD_ManMesh2 &mesh,
        std::vector<LOD_EdgeInd> &e_v0v1,
        LOD_EdgeInd collapse_edge
    );

    // here's the definition of the sort function
    // we use to determine coincedent edges

    // assumes the edges are normalized i.e. m_verts[0] <= m_verts[1]

    struct less : std::binary_function<LOD_Edge, LOD_Edge, bool> {
            bool 
        operator()(
            const LOD_Edge& a,
            const LOD_Edge& b
        ) const {
                
            if (int(a.m_verts[0]) == int(b.m_verts[0])) {
                return (int(a.m_verts[1]) < int(b.m_verts[1]));
            } else {
                return (int(a.m_verts[0]) < int(b.m_verts[0]));
            }
        }
    };

};

#endif