MeshOptimizers

/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield 
 *
 * This library is open source and may be redistributed and/or modified under  
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or 
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 * 
 * This library 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 
 * OpenSceneGraph Public License for more details.
*/

#ifndef OSGUTIL_MESHOPTIMIZERS
#define OSGUTIL_MESHOPTIMIZERS 1

#include <set>
#include <vector>

#include <osg/Geode>
#include <osg/Geometry>
#include <osg/NodeVisitor>

#include <osgUtil/Optimizer>

namespace osgUtil
{
// Helper that collects all the unique Geometry objects in a subgraph.
class OSGUTIL_EXPORT GeometryCollector : public BaseOptimizerVisitor
{
public:
    GeometryCollector(Optimizer* optimizer,
                      Optimizer::OptimizationOptions options)
        : BaseOptimizerVisitor(optimizer, options) {}
    void reset();
    void apply(osg::Geode& geode);
    typedef std::set<osg::Geometry*> GeometryList;
    GeometryList& getGeometryList() { return _geometryList; };
protected:
    GeometryList _geometryList;
};

// Convert geometry that uses DrawArrays to DrawElements i.e.,
// construct a real mesh. This removes duplicate vertices.
class OSGUTIL_EXPORT IndexMeshVisitor : public GeometryCollector
{
public:
    IndexMeshVisitor(Optimizer* optimizer = 0)
        : GeometryCollector(optimizer, Optimizer::INDEX_MESH)
    {
    }
    void makeMesh(osg::Geometry& geom);
    void makeMesh();
};

// Optimize the triangle order in a mesh for best use of the GPU's
// post-transform cache. This uses Tom Forsyth's algorithm described
// at http://home.comcast.net/~tom_forsyth/papers/fast_vert_cache_opt.html
class OSGUTIL_EXPORT VertexCacheVisitor : public GeometryCollector
{
public:
    VertexCacheVisitor(Optimizer* optimizer = 0)
        : GeometryCollector(optimizer, Optimizer::VERTEX_POSTTRANSFORM)
    {
    }

    void optimizeVertices(osg::Geometry& geom);
    void optimizeVertices();
private:
    void doVertexOptimization(osg::Geometry& geom,
                              std::vector<unsigned>& vertDrawList);
};

// Gather statistics on post-transform cache misses for geometry
class OSGUTIL_EXPORT VertexCacheMissVisitor : public osg::NodeVisitor
{
public:
    VertexCacheMissVisitor(unsigned cacheSize = 16);
    void reset();
    virtual void apply(osg::Geode& geode);
    void doGeometry(osg::Geometry& geom);
    unsigned misses;
    unsigned triangles;
protected:
    const unsigned _cacheSize;
};

// Optimize the use of the GPU pre-transform cache by arranging vertex
// attributes in the order they are used.
class OSGUTIL_EXPORT VertexAccessOrderVisitor : public GeometryCollector
{
public:
    VertexAccessOrderVisitor(Optimizer* optimizer = 0)
        : GeometryCollector(optimizer, Optimizer::VERTEX_PRETRANSFORM)
    {
    }
    void optimizeOrder();
    void optimizeOrder(osg::Geometry& geom);
};
}
#endif