/*
   This file is part of the VRender library.
   Copyright (C) 2005 Cyril Soler (Cyril.Soler@imag.fr)
   Version 1.0.0, released on June 27, 2005.

   http://artis.imag.fr/Members/Cyril.Soler/VRender

   VRender 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.

   VRender 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 VRender; if not, write to the Free Software Foundation, Inc.,
   59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 */

/****************************************************************************

   Copyright (C) 2002-2008 Gilles Debunne. All rights reserved.

   This file is part of the QGLViewer library version 2.3.5.

   http://www.libqglviewer.com - contact@libqglviewer.com

   This file may be used under the terms of the GNU General Public License
   versions 2.0 or 3.0 as published by the Free Software Foundation and
   appearing in the LICENSE file included in the packaging of this file.
   In addition, as a special exception, Gilles Debunne gives you certain
   additional rights, described in the file GPL_EXCEPTION in this package.

   libQGLViewer uses dual licensing. Commercial/proprietary software must
   purchase a libQGLViewer Commercial License.

   This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
   WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

 *****************************************************************************/

#include <vector>
#include "VRender.h"
#include "Optimizer.h"
#include "Primitive.h"

using namespace std;
using namespace vrender;

// Over-simplified algorithm to check wether a polygon is front-facing or not.
// Only works for convex polygons.

void BackFaceCullingOptimizer::optimize(std::vector<PtrPrimitive>& primitives_tab, VRenderParams&)
{
  Polygone* P;
  int nb_culled = 0;

  for(unsigned int i = 0; i < primitives_tab.size(); ++i)
    if((P = dynamic_cast<Polygone*>(primitives_tab[i])) != NULL) {
      for(int j = 0; j < P->nbVertices(); ++j)
        if(((P->vertex(j + 2) - P->vertex(j + 1)) ^ (P->vertex(j + 1) - P->vertex(j))).z() > 0.0) {
          delete primitives_tab[i];
          primitives_tab[i] = NULL;
          ++nb_culled;
          break;
        }
    }

  // Rule out gaps. This avoids testing for null primitives later.

  int j = 0;
  for(unsigned int k = 0; k < primitives_tab.size(); ++k)
    if(primitives_tab[k] != NULL)
      primitives_tab[j++] = primitives_tab[k];

  primitives_tab.resize(j);
#ifdef DEBUG_BFC
  cout << "Backface culling: " << nb_culled << " polygons culled." << endl;
#endif
}
