/* -*-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_FLUIDPROGRAM
#define OSGPARTICLE_FLUIDPROGRAM 1

#include <osgParticle/Export>
#include <osgParticle/Program>

#include <osg/CopyOp>
#include <osg/Object>
#include <osg/Node>
#include <osg/NodeVisitor>

namespace osgParticle
{

    /**    A program class for performing operations on particles using a sequence of <I>operators</I>.
        To use a <CODE>FluidProgram</CODE> you have to create some <CODE>Operator</CODE> objects and
        add them to the program.
        All operators will be applied to each particle in the same order they've been added to the program.
    */
    class OSGPARTICLE_EXPORT FluidProgram: public Program {
    public:
        FluidProgram();
        FluidProgram(const FluidProgram& copy, const osg::CopyOp& copyop = osg::CopyOp::SHALLOW_COPY);

        META_Node(osgParticle,FluidProgram);

        /// Set the viscosity of the fluid.
        inline void setFluidViscosity(float v)
        {
            _viscosity = v;
            _viscosityCoefficient = 6 * osg::PI * _viscosity;
        }

        /// Get the viscosity of the fluid.
        inline float getFluidViscosity() const { return _viscosity; }

        /// Set the density of the fluid.
        inline void setFluidDensity(float d)
        {
            _density = d;
            _densityCoefficient = 0.2f * osg::PI * _density;
        }

        /// Get the density of the fluid.
        inline float getFluidDensity() const { return _density; }


        /// Set the wind vector.
        inline void setWind(const osg::Vec3& wind) { _wind = wind; }

        /// Get the wind vector.
        inline const osg::Vec3& getWind() const { return _wind; }

        /// Set the acceleration vector.
        inline void setAcceleration(const osg::Vec3& v) { _acceleration = v; }

        /// Get the acceleration vector.
        inline const osg::Vec3& getAcceleration() const { return _acceleration; }

        /** Set the acceleration vector to the gravity on earth (0, 0, -9.81).
            The acceleration will be multiplied by the <CODE>scale</CODE> parameter.
        */
        inline void setToGravity(float scale = 1.0f) { _acceleration.set(0, 0, -9.81f*scale); }

        /// Set the fluid parameters as for air (20°C temperature).
        inline void setFluidToAir()
        {
            setToGravity(1.0f);
            setFluidDensity(1.2929f);
            setFluidViscosity(1.8e-5f);
        }

        /// Set the fluid parameters as for pure water (20°C temperature).
        inline void setFluidToWater()
        {
            setToGravity(1.0f);
            setFluidDensity(1.0f);
            setFluidViscosity(1.002e-3f);
        }


    protected:

        virtual ~FluidProgram() {}
        FluidProgram& operator=(const FluidProgram&) { return *this; }

        virtual void execute(double dt);

        osg::Vec3   _acceleration;
        float       _viscosity;
        float       _density;
        osg::Vec3   _wind;

        float       _viscosityCoefficient;
        float       _densityCoefficient;
    };


}

#endif
