paysages3d/lib_paysages/atmosphere/preetham.c
2013-01-20 21:17:03 +00:00

135 lines
4.2 KiB
C

#include "public.h"
#include "private.h"
#include <math.h>
#include <assert.h>
#include "../renderer.h"
static inline double _angleBetween(double thetav, double phiv, double theta, double phi)
{
double cospsi = sin(thetav) * sin(theta) * cos(phi-phiv) + cos(thetav) * cos(theta);
if (cospsi > 1.0) return 0.0;
if (cospsi < -1.0) return M_PI;
return acos(cospsi);
}
static inline Color _xyYToRGB(double x, double y, double Y)
{
double fX, fY, fZ;
Color result;
fY = Y;
fX = x / y * Y;
fZ = ((1.0 - x - y) / y) * Y;
double r, g, b;
r = 3.2404 * fX - 1.5371 * fY - 0.4985 * fZ;
g = -0.9692 * fX + 1.8759 * fY + 0.0415 * fZ;
b = 0.0556 * fX - 0.2040 * fY + 1.0573 * fZ;
double expo = -(1.0 / 10000.0);
r = 1.0 - exp(expo * r);
g = 1.0 - exp(expo * g);
b = 1.0 - exp(expo * b);
if (r < 0.0) r = 0.0;
if (g < 0.0) g = 0.0;
if (b < 0.0) b = 0.0;
result.r = r;
result.g = g;
result.b = b;
result.a = 1.0;
return result;
}
static inline void _directionToThetaPhi(Vector3 direction, double* theta, double* phi)
{
direction = v3Normalize(direction);
*phi = atan2(-direction.z, direction.x);
*theta = M_PI_2 - asin(direction.y);
}
Color preethamGetSkyColor(AtmosphereDefinition* definition, Vector3 eye, Vector3 direction, Vector3 sun_position)
{
double theta, phi;
double thetaSun, phiSun;
_directionToThetaPhi(direction, &theta, &phi);
_directionToThetaPhi(sun_position, &thetaSun, &phiSun);
if (theta > M_PI / 2.0)
{
theta = M_PI / 2.0;
}
double gamma = _angleBetween(theta, phi, thetaSun, phiSun);
double cosTheta;
if (theta > M_PI / 2.0)
{
cosTheta = 0.0000001;
}
else
{
cosTheta = cos(theta);
}
double T = definition->humidity * 3.0 + 1.8;
double T2 = T * T;
double suntheta = thetaSun;
double suntheta2 = thetaSun * thetaSun;
double suntheta3 = thetaSun * suntheta2;
double Ax = -0.01925 * T - 0.25922;
double Bx = -0.06651 * T + 0.00081;
double Cx = -0.00041 * T + 0.21247;
double Dx = -0.06409 * T - 0.89887;
double Ex = -0.00325 * T + 0.04517;
double Ay = -0.01669 * T - 0.26078;
double By = -0.09495 * T + 0.00921;
double Cy = -0.00792 * T + 0.21023;
double Dy = -0.04405 * T - 1.65369;
double Ey = -0.01092 * T + 0.05291;
double AY = 0.17872 * T - 1.46303;
double BY = -0.35540 * T + 0.42749;
double CY = -0.02266 * T + 5.32505;
double DY = 0.12064 * T - 2.57705;
double EY = -0.06696 * T + 0.37027;
double cosGamma = cos(gamma);
cosGamma = cosGamma < 0.0 ? 0.0 : cosGamma;
double cosSTheta = fabs(cos(thetaSun));
double xz = ( 0.00165 * suntheta3 - 0.00375 * suntheta2 + 0.00209 * suntheta + 0.00000) * T2 +
(-0.02903 * suntheta3 + 0.06377 * suntheta2 - 0.03202 * suntheta + 0.00394) * T +
( 0.11693 * suntheta3 - 0.21196 * suntheta2 + 0.06052 * suntheta + 0.25886);
double yz = ( 0.00275 * suntheta3 - 0.00610 * suntheta2 + 0.00317 * suntheta + 0.00000) * T2 +
(-0.04214 * suntheta3 + 0.08970 * suntheta2 - 0.04153 * suntheta + 0.00516) * T +
( 0.15346 * suntheta3 - 0.26756 * suntheta2 + 0.06670 * suntheta + 0.26688);
double X = (4.0 / 9.0 - T / 120.0) * (M_PI - 2.0 * suntheta);
double Yz = ((4.0453 * T - 4.9710) * tan(X) - 0.2155 * T + 2.4192) * 1000.0;
double val1, val2;
val1 = (1.0 + Ax * exp(Bx / cosTheta)) * (1.0 + Cx * exp(Dx * gamma) + Ex * sqrt(cosGamma));
val2 = (1.0 + Ax * exp(Bx)) * (1.0 + Cx * exp(Dx * suntheta) + Ex * sqrt(cosSTheta));
double x = xz * val1 / val2;
val1 = (1.0 + Ay * exp(By / cosTheta)) * (1.0 + Cy * exp(Dy * gamma) + Ey * sqrt(cosGamma));
val2 = (1.0 + Ay * exp(By)) * (1.0 + Cy * exp(Dy * suntheta) + Ey * sqrt(cosSTheta));
double y = yz * val1 / val2;
val1 = (1.0 + AY * exp(BY / cosTheta)) * (1.0 + CY * exp(DY * gamma) + EY * sqrt(cosGamma));
val2 = (1.0 + AY * exp(BY)) * (1.0 + CY * exp(DY * suntheta) + EY * sqrt(cosSTheta));
double Y = Yz * val1 / val2;
Color result = _xyYToRGB(x, y, Y);
Color humidity_color = {0.8, 0.8, 0.8, definition->humidity * 0.8 * colorGetValue(&result)};
colorMask(&result, &humidity_color);
return result;
}