/home/cube/sources/osgearth/src/osgEarthDrivers/engine_osgterrain/DynamicLODScaleCallback

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/* -*-c++-*- */
/* osgEarth - Dynamic map generation toolkit for OpenSceneGraph
* Copyright 2008-2010 Pelican Mapping
* http://osgearth.org
*
* osgEarth is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser 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,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program.  If not, see <http://www.gnu.org/licenses/>
*/

#ifndef OSGEARTH_ENGINE_OSGTERRAIN_DYNAMIC_LOD_SCALE_CALLBACK_H
#define OSGEARTH_ENGINE_OSGTERRAIN_DYNAMIC_LOD_SCALE_CALLBACK_H 1

#include <osg/NodeCallback>
#include <osg/CullStack>

struct DynamicLODScaleCallback : public osg::NodeCallback 
{
    DynamicLODScaleCallback( float fallOff ) : _fallOff(fallOff) { }

    void operator()( osg::Node* node, osg::NodeVisitor* nv )
    {
        osg::CullStack* cs = dynamic_cast<osg::CullStack*>(nv);
        if ( cs )
        {
            osg::LOD* lod = static_cast<osg::LOD*>( node );
            osg::Vec3 center = lod->getCenter(); 

            osg::Vec3 eye = nv->getEyePoint();
            osg::Vec3 eyeVec = eye; eyeVec.normalize();
            float has = osg::clampAbove( eye.length() - 6356752.3142f, 0.0f );
            float centerToEye = nv->getDistanceToViewPoint(center, false);
            float bsToEye = centerToEye - lod->getChild(0)->getBound().radius();

            float scaleAdj = 1.0f;
            if ( bsToEye > has )
            {
                float denom = osg::maximum(0.1f, (1.0f/_fallOff)) * 10000.0f;
                scaleAdj = osg::clampBetween( log10f(bsToEye/denom), 1.0f, 3.0f );
                
                //OE_INFO << LC 
                //    << std::fixed
                //    << "centerToEye=" << centerToEye 
                //    << ", bsToEye=" << bsToEye
                //    << ", scaleAdj=" << scaleAdj
                //    << std::endl;
            }

            float lodScale = cs->getLODScale();
            cs->setLODScale( lodScale * scaleAdj );
            traverse( node, nv );
            cs->setLODScale( lodScale );
        }
        else
        {
            traverse( node, nv );
        }
    }

    float _fallOff;
};

#endif //OSGEARTH_ENGINE_OSGTERRAIN_DYNAMIC_LOD_SCALE_CALLBACK_H