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paysages : Preetham approximation for sky (WIP).

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git-svn-id: https://subversion.assembla.com/svn/thunderk/paysages@354 b1fd45b6-86a6-48da-8261-f70d1f35bdcc
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Michaël Lemaire 2012-06-20 20:29:58 +00:00 committed by ThunderK
parent f93f97ed38
commit 9e21a37c04
1 changed files with 174 additions and 2 deletions
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176
lib_paysages/sky.c
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@ -150,18 +150,190 @@ int skyGetLights(SkyDefinition* sky, LightDefinition* lights, int max_lights)
return nblights;
}
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 double _perezFunction(double A, double B, double C, double D, double E, double Theta, double Gamma)
{
double cosGamma = cos(Gamma);
return (1.0 + A * exp(B / cos(Theta))) * (1.0 + C * exp(D * Gamma) + E * cosGamma * cosGamma);
}
typedef struct
{
double x;
double y;
double Y;
} ColorxyY;
/* Distribution coefficients for the luminance(Y) distribution function */
static double YDC[5][2] = { { 0.1787, - 1.4630},
{-0.3554, 0.4275},
{-0.0227, 5.3251},
{ 0.1206, - 2.5771},
{-0.0670, 0.3703} };
/* Distribution coefficients for the x distribution function */
static double xDC[5][2] = { {-0.0193, -0.2592},
{-0.0665, 0.0008},
{-0.0004, 0.2125},
{-0.0641, -0.8989},
{-0.0033, 0.0452} };
/* Distribution coefficients for the y distribution function */
static double yDC[5][2] = { {-0.0167, -0.2608},
{-0.0950, 0.0092},
{-0.0079, 0.2102},
{-0.0441, -1.6537},
{-0.0109, 0.0529} };
/* Zenith x value */
static double xZC[3][4] = { {0.00166, -0.00375, 0.00209, 0},
{-0.02903, 0.06377, -0.03203, 0.00394},
{0.11693, -0.21196, 0.06052, 0.25886} };
/* Zenith y value */
static double yZC[3][4] = { { 0.00275, -0.00610, 0.00317, 0},
{-0.04214, 0.08970, -0.04153, 0.00516},
{0.15346, -0.26756, 0.06670, 0.26688} };
static double _distribution(double A, double B, double C, double D, double E, double Theta, double Gamma, double ThetaSun)
{
double f0 = _perezFunction(A,B,C,D,E,Theta,Gamma);
double f1 = _perezFunction(A,B,C,D,E,0,ThetaSun);
return(f0/f1);
}
static double _chromaticity( double ZC[3][4], double ThetaSun, double turbidity)
{
double t1 = ThetaSun;
double t2 = t1*t1;
double t3 = t2 * t1;
double c = (ZC[0][0]*t3 + ZC[0][1]*t2 + ZC[0][2]*t1 + ZC[0][3])* turbidity * turbidity +
(ZC[1][0]*t3 + ZC[1][1]*t2 + ZC[1][2]*t1 + ZC[1][3])* turbidity +
(ZC[2][0]*t3 + ZC[2][1]*t2 + ZC[2][2]*t1 + ZC[2][3]);
return c;
}
static Color _toColor(ColorxyY src)
{
double X, Y, Z;
Color dest;
/* Convert to XYZ space */
X = src.x * (src.Y / src.y);
Y = src.Y;
Z = (1.0 - src.x - src.y)* (src.Y/src.y);
/* Convert to RGB */
dest.r = 3.240479 * X - 1.537150 * Y - 0.498535 * Z;
dest.g = - 0.969256 * X + 1.875991 * Y + 0.041556 * Z;
dest.b = 0.055648 * X - 0.204043 * Y + 1.057311 * Z;
dest.a = 1.0;
return dest;
}
static Color _preethamApproximate(SkyDefinition* definition, double theta, double phi)
{
double thetaSun;
double phiSun;
double gamma;
double turbidity = 3.0;
ColorxyY skycolor;
ColorxyY Zenith;
double A,B,C,D,E;
double d,chi;
/* Handle angles */
if (definition->daytime <= 0.5)
{
if (definition->daytime <= 0.25)
{
thetaSun = M_PI / 2.0 - 0.00001;
}
else
{
thetaSun = M_PI - definition->daytime * 2.0 * M_PI;
}
phiSun = 0.0;
}
else
{
if (definition->daytime >= 0.75)
{
thetaSun = M_PI / 2.0 - 0.00001;
}
else
{
thetaSun = (definition->daytime - 0.5) * 2.0 * M_PI;
}
phiSun = M_PI;
}
gamma = _angleBetween(theta, phi, thetaSun, phiSun);
/* Zenith luminance */
chi = (4.0/9.0 - turbidity/120.0)*(M_PI - 2*thetaSun);
Zenith.Y = (4.0453*turbidity - 4.9710)*tan(chi) - 0.2155*turbidity + 2.4192;
if (Zenith.Y < 0.0) Zenith.Y = -Zenith.Y;
A = YDC[0][0]*turbidity + YDC[0][1];
B = YDC[1][0]*turbidity + YDC[1][1];
C = YDC[2][0]*turbidity + YDC[2][1];
D = YDC[3][0]*turbidity + YDC[3][1];
E = YDC[4][0]*turbidity + YDC[4][1];
/* Sky luminance */
d = _distribution(A, B, C, D, E, theta, gamma, thetaSun);
skycolor.Y = Zenith.Y * d;
/* Zenith x */
Zenith.x = _chromaticity( xZC, thetaSun, turbidity );
A = xDC[0][0]*turbidity + xDC[0][1];
B = xDC[1][0]*turbidity + xDC[1][1];
C = xDC[2][0]*turbidity + xDC[2][1];
D = xDC[3][0]*turbidity + xDC[3][1];
E = xDC[4][0]*turbidity + xDC[4][1];
/* Sky x */
d = _distribution(A, B, C, D, E, theta, gamma, thetaSun);
skycolor.x = Zenith.x * d;
/* Zenith y */
Zenith.y = _chromaticity( yZC, thetaSun, turbidity );
A = yDC[0][0]*turbidity + yDC[0][1];
B = yDC[1][0]*turbidity + yDC[1][1];
C = yDC[2][0]*turbidity + yDC[2][1];
D = yDC[3][0]*turbidity + yDC[3][1];
E = yDC[4][0]*turbidity + yDC[4][1];
/* Sky y */
d = _distribution(A, B, C, D, E, theta, gamma, thetaSun);
skycolor.y = Zenith.y * d;
/* Small hack on luminance value */
//skycolor.Y = 1 - exp(-(1.0/25.0) * skycolor.Y);
return _toColor(skycolor);
}
Color skyGetColor(SkyDefinition* definition, Renderer* renderer, Vector3 eye, Vector3 look)
{
double dist;
Vector3 sun_position;
Color sun_color, sky_color;
sun_position = skyGetSunDirection(definition);
look = v3Normalize(look);
dist = v3Norm(v3Sub(look, sun_position));
sky_color = colorGradationGet(definition->_sky_gradation, look.y * 0.5 + 0.5);
sky_color = _preethamApproximate(definition, M_PI/2.0 - asin(look.y), acos(v3Dot(look, sun_position)));
if (dist < definition->sun_radius + definition->sun_halo_size)
{
sun_color = colorGradationGet(definition->sun_color, definition->daytime);