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LOD_EdgeCollapser.h

/**
 * $Id: LOD_EdgeCollapser.h,v 1.5 2002/12/26 18:25:08 mein Exp $
 * ***** BEGIN GPL/BL DUAL 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. The Blender
 * Foundation also sells licenses for use in proprietary software under
 * the Blender License.  See http://www.blender.org/BL/ for information
 * about this.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * 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., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * The Original Code is Copyright (C) 2001-2002 by NaN Holding BV.
 * All rights reserved.
 *
 * The Original Code is: all of this file.
 *
 * Contributor(s): none yet.
 *
 * ***** END GPL/BL DUAL LICENSE BLOCK *****
 */

#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


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