Checked in osgParticle, writtten by Marco Jez.

include/osgParticle/ForceOperator

@@ -0,0 +1,89 @@
+//C++ header - Open Scene Graph - Copyright (C) 1998-2002 Robert Osfield
+//Distributed under the terms of the GNU Library General Public License (LGPL)
+//as published by the Free Software Foundation.
+//osgParticle - Copyright (C) 2002 Marco Jez
+
+#ifndef OSGPARTICLE_FORCEOPERATOR_
+#define OSGPARTICLE_FORCEOPERATOR_ 1
+
+#include <osgParticle/ModularProgram>
+#include <osgParticle/Operator>
+#include <osgParticle/Particle>
+
+#include <osg/CopyOp>
+#include <osg/Object>
+#include <osg/Vec3>
+
+namespace osgParticle
+{
+
+    /**    An operator that applies a constant force to the particles.
+        Remember that if the mass of particles is expressed in <U>kg</U> and the lengths are
+        expressed in <U>meters</U>, then the force should be expressed in <U>Newtons</U>.
+    */
+    class ForceOperator: public Operator {
+    public:
+        inline ForceOperator();
+        inline ForceOperator(const ForceOperator &copy, const osg::CopyOp &copyop = osg::CopyOp::SHALLOW_COPY);
+        
+        META_Object(ForceOperator);
+        
+        /// Get the force vector.
+        inline const osg::Vec3 &getForce() const;
+        
+        /// Set the force vector.
+        inline void setForce(const osg::Vec3 &f);
+        
+        /// Apply the force to a particle. Do not call this method manually.
+        inline void operate(Particle *P, double dt);
+        
+        /// Perform some initialization. Do not call this method manually.
+        inline void beginOperate(Program *prg);
+        
+    protected:
+        virtual ~ForceOperator() {};
+        ForceOperator &operator=(const ForceOperator &) { return *this; }        
+        
+    private:
+        osg::Vec3 force_;
+        osg::Vec3 xf_force_;
+    };
+    
+    // INLINE FUNCTIONS
+    
+    inline ForceOperator::ForceOperator()
+    : Operator(), force_(0, 0, 0)
+    {        
+    }
+    
+    inline ForceOperator::ForceOperator(const ForceOperator &copy, const osg::CopyOp &copyop)
+    : Operator(copy, copyop), force_(copy.force_)
+    {
+    }
+    
+    inline const osg::Vec3 &ForceOperator::getForce() const
+    {
+        return force_;
+    }
+    
+    inline void ForceOperator::setForce(const osg::Vec3 &v)
+    {
+        force_ = v;
+    }
+    
+    inline void ForceOperator::operate(Particle *P, double dt)
+    {
+        P->addVelocity(xf_force_ * (P->getMassInv() * dt));
+    }
+    
+    inline void ForceOperator::beginOperate(Program *prg)
+    {
+        if (prg->getReferenceFrame() == ModularProgram::RELATIVE_TO_PARENTS) {
+            xf_force_ = prg->rotateLocalToWorld(force_);
+        } else {
+            xf_force_ = force_;
+        }
+    }
+}
+
+#endif