ConstantRateCounter

/* -*-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 OSGPARTICLE_CONSTANTRATECOUNTER
#define OSGPARTICLE_CONSTANTRATECOUNTER 1

#include <osgParticle/Counter>

#include <osg/Object>
#include <osg/Math>

namespace osgParticle
{

    class ConstantRateCounter: public Counter {
    public:
        ConstantRateCounter():
            Counter(), 
            _minimumNumberOfParticlesToCreate(0),
            _numberOfParticlesPerSecondToCreate(0),
            _carryOver(0)
        {
        }

        ConstantRateCounter(const ConstantRateCounter& copy, const osg::CopyOp& copyop = osg::CopyOp::SHALLOW_COPY):
             Counter(copy, copyop), 
             _minimumNumberOfParticlesToCreate(copy._minimumNumberOfParticlesToCreate),
             _numberOfParticlesPerSecondToCreate(copy._numberOfParticlesPerSecondToCreate),
             _carryOver(copy._carryOver)
        {
        }
            
        
        META_Object(osgParticle, ConstantRateCounter);
        
        void setMinimumNumberOfParticlesToCreate(int minNumToCreate) { _minimumNumberOfParticlesToCreate = minNumToCreate; }
        int getMinimumNumberOfParticlesToCreate() const { return _minimumNumberOfParticlesToCreate; }
    
        void setNumberOfParticlesPerSecondToCreate(double numPerSecond) { _numberOfParticlesPerSecondToCreate = numPerSecond; }
        double getNumberOfParticlesPerSecondToCreate() const { return _numberOfParticlesPerSecondToCreate; }

        /// Return the number of particles to be created in this frame
        virtual int numParticlesToCreate(double dt) const
        {
            double v = (dt*_numberOfParticlesPerSecondToCreate);
            int i = (int)(v);
            _carryOver += (v-(double)i);
            if (_carryOver>1.0)
            {
                ++i;
                _carryOver -= 1.0;
            }
            return osg::maximum(_minimumNumberOfParticlesToCreate, i);
        }
        
    protected:
        virtual ~ConstantRateCounter() {}
        
        int _minimumNumberOfParticlesToCreate;
        double _numberOfParticlesPerSecondToCreate;
        mutable double _carryOver;
    };
    
}


#endif