/**
 * @file precipitation.cxx
 * @author Nicolas VIVIEN
 * @date 2008-02-10
 *
 * @note Copyright (C) 2008 Nicolas VIVIEN
 *
 * @brief Precipitation effects to draw rain and snow.
 *
 * @par Licences
 *   This program is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU General Public License as
 *   published by the Free Software Foundation; either version 2 of the
 *   License, or (at your option) any later version.
 *
 *   This program 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 GNU
 *   General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 */

#include "precipitation.hxx"
#include "visual_enviro.hxx"

#include <simgear/constants.h>
#include <osg/ClipNode>

/**
 * @brief SGPrecipitation constructor
 *
 * Build a new OSG object from osgParticle.
 */
SGPrecipitation::SGPrecipitation() :
    _freeze(false), _snow_intensity(0.0), _rain_intensity(0.0), _clip_distance(5.0)
{
    _precipitationEffect = new osgParticle::PrecipitationEffect;
}


/**
 * @brief Build and add the object "precipitationEffect"
 *
 * This function permits you to create an object precipitationEffect and initialize it.
 * I define by default the color of water (for raining)
 */
osg::Group* SGPrecipitation::build(void)
{
    osg::Group* group = new osg::Group;

    _precipitationEffect->snow(0);	
    _precipitationEffect->rain(0);	

    if (_clip_distance!=0.0)
    {    
        osg::ref_ptr<osg::ClipNode> clipNode = new osg::ClipNode;
        clipNode->addClipPlane( new osg::ClipPlane( 0 ) );
        clipNode->getClipPlane(0)->setClipPlane( 0.0, 0.0, -1.0, -_clip_distance );
        clipNode->setReferenceFrame(osg::ClipNode::ABSOLUTE_RF);
        clipNode->addChild(_precipitationEffect.get());

        group->addChild(clipNode.get());
    }
    else
    {
        group->addChild(_precipitationEffect.get());
    }

    return group;
}


/**
 * @brief Define the snow intensity
 *
 * This function permits you to define and change the snow intensity
 * The param 'intensity' is normed (0 to 1).
 */
void SGPrecipitation::setSnowIntensity(float intensity)
{
    if (this->_snow_intensity < intensity-0.001)
        this->_snow_intensity += 0.001;
    else if (this->_snow_intensity > intensity+0.001)
        this->_snow_intensity -= 0.001;
    else
        this->_snow_intensity = intensity;
}


/**
 * @brief Define the rain intensity
 *
 * This function permits you to define and change the rain intensity
 * The param 'intensity' is normed (0 to 1).
 */
void SGPrecipitation::setRainIntensity(float intensity)
{
    if (this->_rain_intensity < intensity-0.001)
        this->_rain_intensity += 0.001;
    else if (this->_rain_intensity > intensity+0.001)
        this->_rain_intensity -= 0.001;
    else
        this->_rain_intensity = intensity;
}


/** 
 * @brief Freeze the rain to snow
 * 
 * @param freeze Boolean 
 * 
 * This function permits you to turn off the rain to snow.
 */
void SGPrecipitation::setFreezing(bool freeze)
{
    this->_freeze = freeze;
}


/**
 * @brief Define the wind direction and speed
 *
 * This function permits you to define and change the wind direction
 * 
 * After apply the MatrixTransform to the osg::Precipitation object,
 * x points full south... From wind heading and speed, we can calculate
 * the wind vector.
 */
void SGPrecipitation::setWindProperty(double heading, double speed)
{
    double x, y, z;

    heading = (heading + 180) * SGD_DEGREES_TO_RADIANS;
    speed = speed * SG_FEET_TO_METER;

    x = -cos(heading) * speed;
    y = sin(heading) * speed;
    z = 0;

    this->_wind_vec = osg::Vec3(x, y, z);
}


/**
 * @brief Update the precipitation effects
 *
 * This function permits you to update the precipitation effects.
 * Be careful, if snow and rain intensity are greater than '0', snow effect
 * will be first.
 *
 * The settings come from the osgParticule/PrecipitationEffect.cpp exemple.
 */
bool SGPrecipitation::update(void)
{
    if (this->_freeze) {
        if (this->_rain_intensity > 0) 
            this->_snow_intensity = this->_rain_intensity;
    }

    bool enabled = sgEnviro.get_precipitation_enable_state();
    if (enabled && this->_snow_intensity > 0) {
        _precipitationEffect->setWind(_wind_vec);
        _precipitationEffect->setParticleSpeed( -0.75f - 0.25f*_snow_intensity);
		
        _precipitationEffect->setParticleSize(0.02f + 0.03f*_snow_intensity);
        _precipitationEffect->setMaximumParticleDensity(_snow_intensity * 7.2f);
        _precipitationEffect->setCellSize(osg::Vec3(5.0f / (0.25f+_snow_intensity), 5.0f / (0.25f+_snow_intensity), 5.0f));
		
        _precipitationEffect->setNearTransition(25.f);
        _precipitationEffect->setFarTransition(100.0f - 60.0f*sqrtf(_snow_intensity));
		
        _precipitationEffect->setParticleColor(osg::Vec4(0.85, 0.85, 0.85, 1.0) - osg::Vec4(0.1, 0.1, 0.1, 1.0) * _snow_intensity);
    } else if (enabled && this->_rain_intensity > 0) {
        _precipitationEffect->setWind(_wind_vec);
        _precipitationEffect->setParticleSpeed( -2.0f + -5.0f*_rain_intensity);
		
        _precipitationEffect->setParticleSize(0.01 + 0.02*_rain_intensity);
        _precipitationEffect->setMaximumParticleDensity(_rain_intensity * 7.5f);
        _precipitationEffect->setCellSize(osg::Vec3(5.0f / (0.25f+_rain_intensity), 5.0f / (0.25f+_rain_intensity), 5.0f));
		
        _precipitationEffect->setNearTransition(25.f);
        _precipitationEffect->setFarTransition(100.0f - 60.0f*sqrtf(_rain_intensity));
		
        _precipitationEffect->setParticleColor( osg::Vec4(0x7A, 0xCE, 0xFF, 0x80));
    } else {
        _precipitationEffect->snow(0);	
        _precipitationEffect->rain(0);	
    }

    return true;
}
