root/OpenSceneGraph/trunk/src/osgParticle/FluidFrictionOperator.cpp @ 13041

#include <osgParticle/FluidFrictionOperator>
#include <osgParticle/ModularProgram>
#include <osgParticle/Operator>
#include <osgParticle/Particle>
#include <osg/Notify>

osgParticle::FluidFrictionOperator::FluidFrictionOperator():
     Operator(),
     _coeff_A(0),
     _coeff_B(0),
     _density(0),
     _viscosity(0),
     _ovr_rad(0),
     _current_program(0)
{
    setFluidToAir();
}

osgParticle::FluidFrictionOperator::FluidFrictionOperator(const FluidFrictionOperator& copy, const osg::CopyOp& copyop)
:    Operator(copy, copyop),
    _coeff_A(copy._coeff_A),
    _coeff_B(copy._coeff_B),
    _density(copy._density),
    _viscosity(copy._viscosity),
    _ovr_rad(copy._ovr_rad),
    _current_program(0)
{
}

void osgParticle::FluidFrictionOperator::operate(Particle* P, double dt)
{
    float r = (_ovr_rad > 0)? _ovr_rad : P->getRadius();
    osg::Vec3 v = P->getVelocity()-_wind;

    float vm = v.normalize();
    float R = _coeff_A * r * vm + _coeff_B * r * r * vm * vm;

    osg::Vec3 Fr(-R * v.x(), -R * v.y(), -R * v.z());

#if 0
    // Commenting out rotation of force vector rotation from local to world as the particle velocity itself
    // should already be in world coords so shouldn't need rotating.
    if (_current_program->getReferenceFrame() == ModularProgram::RELATIVE_RF) {
        Fr = _current_program->rotateLocalToWorld(Fr);
    }
#endif

    // correct unwanted velocity increments
    osg::Vec3 dv = Fr * P->getMassInv() * dt;
    float dvl = dv.length();
    if (dvl > vm) {
        dv *= vm / dvl;
    }

    P->addVelocity(dv);
}