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Added clamping of the wind force contribution to acceletion of particle so

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that the de-acceleration never exceed the actual wind vector itself.
This commit is contained in:
Robert Osfield
2006-02-24 13:56:07 +00:00
parent 964110f315
commit 4b4c77c420
1 changed files with 16 additions and 7 deletions
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23
src/osgParticle/FluidProgram.cpp
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@@ -32,16 +32,25 @@ void osgParticle::FluidProgram::execute(double dt)
float Volume = Area*radius*four_over_three;
// compute force due to gravity + boyancy of displacing the fluid that the particle is emersed in.
osg::Vec3 force = _acceleration * (particle->getMass() - _density*Volume);
osg::Vec3 accel_gravity = _acceleration * ((particle->getMass() - _density*Volume) * particle->getMassInv());
// compute force due to friction
osg::Vec3 velBefore = particle->getVelocity();
osg::Vec3 relative_wind = particle->getVelocity()-_wind;
force -= relative_wind * Area * (_viscosityCoefficient + _densityCoefficeint*relative_wind.length());
osg::Vec3 wind_force = - relative_wind * Area * (_viscosityCoefficient + _densityCoefficeint*relative_wind.length());
osg::Vec3 wind_accel = wind_force * particle->getMassInv();
double critical_dt2 = relative_wind.length2()/wind_accel.length2();
double compenstated_dt = dt;
if (critical_dt2 < dt*dt)
{
// osg::notify(osg::NOTICE)<<"** Could be critical: dt="<<dt<<" critical_dt="<<sqrtf(critical_dt2)<<std::endl;
compenstated_dt = sqrtf(critical_dt2)*0.8f;
}
particle->addVelocity(accel_gravity*dt + wind_accel*compenstated_dt);
// divide force by mass to get acceleration.
force *= particle->getMassInv()*dt;
particle->addVelocity(force);
}
}
}