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/**
* ***** BEGIN GPL LICENSE BLOCK *****
*
* 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Contributor(s): zaghaghi
*
* ***** END GPL LICENSE BLOCK *****
*/
/**
* This feature comes from Preetham paper on "A Practical Analytic Model for Daylight"
* and example code from Brian Smits, another author of that paper in
* http://www.cs.utah.edu/vissim/papers/sunsky/code/
* */
#ifndef SUNSKY_H_
#define SUNSKY_H_
#define SPECTRUM_MAX_COMPONENTS 100
#define SPECTRUM_START 350.0
#define SPECTRUM_END 800.0
typedef struct SunSky
{
short effect_type;
float turbidity;
float theta, phi;
float toSun[3];
/*float sunSpectralRaddata[SPECTRUM_MAX_COMPONENTS];*/
float sunSolidAngle;
float zenith_Y, zenith_x, zenith_y;
float perez_Y[5], perez_x[5], perez_y[5];
/* suggested by glome in
* http://projects.blender.org/tracker/?func=detail&atid=127&aid=8063&group_id=9*/
float horizon_brightness;
float spread;
float sun_brightness;
float sun_size;
float backscattered_light;
float atm_HGg;
float atm_SunIntensity;
float atm_InscatteringMultiplier;
float atm_ExtinctionMultiplier;
float atm_BetaRayMultiplier;
float atm_BetaMieMultiplier;
float atm_DistanceMultiplier;
float atm_BetaRay[3];
float atm_BetaDashRay[3];
float atm_BetaMie[3];
float atm_BetaDashMie[3];
float atm_BetaRM[3];
}SunSky;
/**
* InitSunSky:
* this function compute some sun,sky parameters according to input parameters and also initiate some other sun, sky parameters
* parameters:
* sunSky, is a structure that contains informtion about sun, sky and atmosphere, in this function, most of its values initiated
* turb, is atmosphere turbidity
* toSun, contains sun direction
* horizon_brighness, controls the brightness of the horizon colors
* spread, controls colors spreed at horizon
* sun_brightness, controls sun's brightness
* sun_size, controls sun's size
* back_scatter, controls back scatter light
* */
void InitSunSky(struct SunSky *sunsky, float turb, float *toSun, float horizon_brightness,
float spread,float sun_brightness, float sun_size, float back_scatter);
/**
* GetSkyXYZRadiance:
* this function compute sky radiance according to a view parameters `theta' and `phi'and sunSky values
* parameters:
* sunSky, sontains sun and sky parameters
* theta, is sun's theta
* phi, is sun's phi
* color_out, is computed color that shows sky radiance in XYZ color format
* */
void GetSkyXYZRadiance(struct SunSky* sunsky, float theta, float phi, float color_out[3]);
/**
* GetSkyXYZRadiancef:
* this function compute sky radiance according to a view direction `varg' and sunSky values
* parameters:
* sunSky, sontains sun and sky parameters
* varg, shows direction
* color_out, is computed color that shows sky radiance in XYZ color format
* */
void GetSkyXYZRadiancef(struct SunSky* sunsky, const float varg[3], float color_out[3]);
/**
* InitAtmosphere:
* this function intiate sunSky structure with user input parameters.
* parameters:
* sunSky, contains information about sun, and in this function some atmosphere parameters will initiated
* sun_intens, shows sun intensity value
* mief, Mie scattering factor this factor currently call with 1.0
* rayf, Rayleigh scattering factor, this factor currently call with 1.0
* inscattf, inscatter light factor that range from 0.0 to 1.0, 0.0 means no inscatter light and 1.0 means full inscatter light
* extincf, extinction light factor that range from 0.0 to 1.0, 0.0 means no extinction and 1.0 means full extinction
* disf, is distance factor, multiplyed to pixle's z value to compute each pixle's distance to camera,
* */
void InitAtmosphere(struct SunSky *sunSky, float sun_intens, float mief, float rayf, float inscattf, float extincf, float disf);
/**
* AtmospherePixleShader:
* this function apply atmosphere effect on a pixle color `rgb' at distance `s'
* parameters:
* sunSky, contains information about sun parameters and user values
* view, is camera view vector
* s, is distance
* rgb, contains rendered color value for a pixle
* */
void AtmospherePixleShader( struct SunSky* sunSky, float view[3], float s, float rgb[3]);
/**
* ClipColor:
* clip a color to range [0,1];
* */
void ClipColor(float c[3]);
#endif /*SUNSKY_H_*/
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