BackFaceCullingOptimizer.cpp
1 /*
2  This file is part of the VRender library.
3  Copyright (C) 2005 Cyril Soler (Cyril.Soler@imag.fr)
4  Version 1.0.0, released on June 27, 2005.
5 
6  http://artis.imag.fr/Members/Cyril.Soler/VRender
7 
8  VRender is free software; you can redistribute it and/or modify
9  it under the terms of the GNU General Public License as published by
10  the Free Software Foundation; either version 2 of the License, or
11  (at your option) any later version.
12 
13  VRender is distributed in the hope that it will be useful,
14  but WITHOUT ANY WARRANTY; without even the implied warranty of
15  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16  GNU General Public License for more details.
17 
18  You should have received a copy of the GNU General Public License
19  along with VRender; if not, write to the Free Software Foundation, Inc.,
20  51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
21 */
22 
23 /****************************************************************************
24 
25  Copyright (C) 2002-2013 Gilles Debunne. All rights reserved.
26 
27  This file is part of the QGLViewer library version 2.5.2.
28 
29  http://www.libqglviewer.com - contact@libqglviewer.com
30 
31  This file may be used under the terms of the GNU General Public License
32  versions 2.0 or 3.0 as published by the Free Software Foundation and
33  appearing in the LICENSE file included in the packaging of this file.
34  In addition, as a special exception, Gilles Debunne gives you certain
35  additional rights, described in the file GPL_EXCEPTION in this package.
36 
37  libQGLViewer uses dual licensing. Commercial/proprietary software must
38  purchase a libQGLViewer Commercial License.
39 
40  This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
41  WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
42 
43 *****************************************************************************/
44 
45 #include <vector>
46 #include "VRender.h"
47 #include "Optimizer.h"
48 #include "Primitive.h"
49 
50 using namespace std ;
51 using namespace vrender ;
52 
53 // Over-simplified algorithm to check wether a polygon is front-facing or not.
54 // Only works for convex polygons.
55 
56 void BackFaceCullingOptimizer::optimize(std::vector<PtrPrimitive>& primitives_tab,VRenderParams&)
57 {
58  Polygone *P ;
59  int nb_culled = 0 ;
60 
61  for(unsigned int i=0;i<primitives_tab.size();++i)
62  if((P = dynamic_cast<Polygone *>(primitives_tab[i])) != NULL)
63  {
64  for(unsigned int j=0;j<P->nbVertices();++j)
65  if(( (P->vertex(j+2) - P->vertex(j+1))^(P->vertex(j+1) - P->vertex(j))).z() > 0.0 )
66  {
67  delete primitives_tab[i] ;
68  primitives_tab[i] = NULL ;
69  ++nb_culled ;
70  break ;
71  }
72  }
73 
74  // Rule out gaps. This avoids testing for null primitives later.
75 
76  int j=0 ;
77  for(unsigned int k=0;k<primitives_tab.size();++k)
78  if(primitives_tab[k] != NULL)
79  primitives_tab[j++] = primitives_tab[k] ;
80 
81  primitives_tab.resize(j) ;
82 #ifdef DEBUG_BFC
83  cout << "Backface culling: " << nb_culled << " polygons culled." << endl ;
84 #endif
85 }