From 05f2c19ef66a5cb9677f00cb6e2af508a8756c4c Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Micha=C3=ABl=20Lemaire?= Date: Thu, 21 Jun 2012 18:21:21 +0000 Subject: [PATCH] paysages : Preetham approximation for sky (WIP). git-svn-id: https://subversion.assembla.com/svn/thunderk/paysages@355 b1fd45b6-86a6-48da-8261-f70d1f35bdcc --- lib_paysages/sky.c | 224 +++++++++++++++++++-------------------------- 1 file changed, 92 insertions(+), 132 deletions(-) diff --git a/lib_paysages/sky.c b/lib_paysages/sky.c index df7b4d4..a963429 100644 --- a/lib_paysages/sky.c +++ b/lib_paysages/sky.c @@ -158,85 +158,38 @@ static inline double _angleBetween(double thetav, double phiv, double theta, dou return acos(cospsi); } -static inline double _perezFunction(double A, double B, double C, double D, double E, double Theta, double Gamma) +static inline Color _toColor(float x, float y, float Y) { - double cosGamma = cos(Gamma); - return (1.0 + A * exp(B / cos(Theta))) * (1.0 + C * exp(D * Gamma) + E * cosGamma * cosGamma); -} + float fX, fY, fZ; + Color result; -typedef struct -{ - double x; - double y; - double Y; -} ColorxyY; + fY = Y; + fX = x / y * Y; + fZ = ((1.0f - x - y) / y) * Y; -/* 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} }; + float r, g, b; + + r = 3.2404f * fX - 1.5371f * fY - 0.4985f * fZ; + g = -0.9692f * fX + 1.8759f * fY + 0.0415f * fZ; + b = 0.0556f * fX - 0.2040f * fY + 1.0573f * fZ; -/* 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} }; + float expo = -(1.0f / 10000.0f); + r = 1.0f - exp(expo * r); + g = 1.0f - exp(expo * g); + b = 1.0f - exp(expo * b); -/* 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} }; + if (r < 0.0f) r = 0.0f; + if (g < 0.0f) g = 0.0f; + if (b < 0.0f) b = 0.0f; -/* 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; + result.r = r; + result.g = g; + result.b = b; + result.a = 1.0; + + colorNormalize(&result); + + return result; } static Color _preethamApproximate(SkyDefinition* definition, double theta, double phi) @@ -244,82 +197,89 @@ static Color _preethamApproximate(SkyDefinition* definition, double theta, doubl double thetaSun; double phiSun; double gamma; - double turbidity = 3.0; - ColorxyY skycolor; - ColorxyY Zenith; - double A,B,C,D,E; - double d,chi; + double turbidity = 2.0; /* Handle angles */ + if (theta > M_PI / 2.0) + { + theta = M_PI / 2.0; + } 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; - } + 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; - } + thetaSun = (definition->daytime - 0.5) * 2.0 * M_PI; phiSun = M_PI; } gamma = _angleBetween(theta, phi, thetaSun, phiSun); + + double cosTheta; + if (theta > M_PI / 2.0) + { + cosTheta = 0.0000001; + } + else + { + cosTheta = cos(theta); + } + + double T = turbidity; + double T2 = T * T; + double suntheta = thetaSun; + double suntheta2 = thetaSun * thetaSun; + double suntheta3 = thetaSun * suntheta2; - /* 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; + 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; - 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]; + 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; - /* Sky luminance */ - d = _distribution(A, B, C, D, E, theta, gamma, thetaSun); - skycolor.Y = Zenith.Y * d; + 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; - /* 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]; + 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); - /* Sky x */ - d = _distribution(A, B, C, D, E, theta, gamma, thetaSun); - skycolor.x = Zenith.x * d; + 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 = (4.0f / 9.0f - T / 120.0f) * (M_PI - 2.0 * suntheta); + double Yz = ((4.0453f * T - 4.9710) * tan(X) - 0.2155 * T + 2.4192) * 1000.0f; - /* 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]; + double val1, val2; + + val1 = ( 1 + Ax * exp(Bx / cosTheta ) ) * ( 1 + Cx * exp(Dx * gamma) + Ex * sqrt(cosGamma) ); + val2 = ( 1 + Ax * exp(Bx) ) * ( 1 + Cx * exp(Dx * suntheta) + Ex * sqrt(cosSTheta) ); + double x = xz * val1 / val2; + + val1 = ( 1 + Ay * exp(By / cosTheta) ) * ( 1 + Cy * exp(Dy * gamma ) + Ey * sqrt(cosGamma ) ); + val2 = ( 1 + Ay * exp(By ) ) * ( 1 + Cy * exp(Dy * suntheta) + Ey * sqrt(cosSTheta) ); + double y = yz * val1 / val2; + + val1 = ( 1 + AY * exp(BY / cosTheta) ) * ( 1 + CY * exp(DY * gamma ) + EY * sqrt(cosGamma) ); + val2 = ( 1 + AY * exp(BY ) ) * ( 1 + CY * exp(DY * suntheta) + EY * sqrt(cosSTheta) ); + double Y = Yz * val1 / val2; - /* 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); + return _toColor(x, y, Y); } Color skyGetColor(SkyDefinition* definition, Renderer* renderer, Vector3 eye, Vector3 look) @@ -333,7 +293,7 @@ Color skyGetColor(SkyDefinition* definition, Renderer* renderer, Vector3 eye, Ve look = v3Normalize(look); dist = v3Norm(v3Sub(look, sun_position)); - sky_color = _preethamApproximate(definition, M_PI/2.0 - asin(look.y), acos(v3Dot(look, sun_position))); + sky_color = _preethamApproximate(definition, M_PI/2.0 - asin(look.y), atan2(-look.z, look.x)); if (dist < definition->sun_radius + definition->sun_halo_size) { sun_color = colorGradationGet(definition->sun_color, definition->daytime);