Checked in osgParticle, writtten by Marco Jez.

src/osgParticle/FluidFrictionOperator.cpp

@@ -0,0 +1,38 @@
+#include <osgParticle/FluidFrictionOperator>
+#include <osgParticle/ModularProgram>
+#include <osgParticle/Operator>
+#include <osgParticle/Particle>
+#include <osg/Notify>
+
+osgParticle::FluidFrictionOperator::FluidFrictionOperator()
+: Operator(), ovr_rad_(0)
+{
+    setFluidToAir();
+}
+
+osgParticle::FluidFrictionOperator::FluidFrictionOperator(const FluidFrictionOperator &copy, const osg::CopyOp &copyop)
+:    Operator(copy, copyop),
+    A_(copy.A_),
+    B_(copy.B_),
+    density_(copy.density_), 
+    viscosity_(copy.viscosity_),
+    ovr_rad_(copy.ovr_rad_)
+{
+}
+
+void osgParticle::FluidFrictionOperator::operate(Particle *P, double dt)
+{
+    float r = (ovr_rad_ > 0)? ovr_rad_ : P->getRadius();
+    osg::Vec3 v = P->getVelocity();
+
+    float vm = v.normalize();
+    float R = A_ * r * vm + B_ * r * r * vm * vm;
+    
+    osg::Vec3 Fr(-R * v.x(), -R * v.y(), -R * v.z());
+
+    if (current_program_->getReferenceFrame() == ModularProgram::RELATIVE_TO_PARENTS) {
+        Fr = current_program_->rotateLocalToWorld(Fr);
+    }
+
+    P->addVelocity(Fr * (P->getMassInv() * dt));
+}