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/*
* Copyright 2011-2013 Blender Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License
*/
#include "stdosl.h"
#include "node_color.h"
struct KernelSunSky {
/* sun direction in spherical and cartesian */
float theta, phi;
vector dir;
/* perez function parameters */
float zenith_Y, zenith_x, zenith_y;
float perez_Y[5], perez_x[5], perez_y[5];
};
float sky_angle_between(float thetav, float phiv, float theta, float phi)
{
float 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);
}
vector sky_spherical_coordinates(vector dir)
{
return vector(acos(dir[2]), atan2(dir[0], dir[1]), 0);
}
float sky_perez_function(float lam[5], float theta, float gamma)
{
float ctheta = cos(theta);
float cgamma = cos(gamma);
return (1.0 + lam[0] * exp(lam[1] / ctheta)) * (1.0 + lam[2] * exp(lam[3] * gamma) + lam[4] * cgamma * cgamma);
}
color sky_xyz_radiance(KernelSunSky sunsky, vector dir)
{
/* convert vector to spherical coordinates */
vector spherical = sky_spherical_coordinates(dir);
float theta = spherical[0];
float phi = spherical[1];
/* angle between sun direction and dir */
float gamma = sky_angle_between(theta, phi, sunsky.theta, sunsky.phi);
/* clamp theta to horizon */
theta = min(theta, M_PI_2 - 0.001);
/* compute xyY color space values */
float x = sunsky.zenith_x * sky_perez_function(sunsky.perez_x, theta, gamma);
float y = sunsky.zenith_y * sky_perez_function(sunsky.perez_y, theta, gamma);
float Y = sunsky.zenith_Y * sky_perez_function(sunsky.perez_Y, theta, gamma);
/* convert to RGB */
color xyz = xyY_to_xyz(x, y, Y);
return xyz_to_rgb(xyz[0], xyz[1], xyz[2]);
}
void precompute_sunsky(vector dir, float turbidity, output KernelSunSky sunsky)
{
vector spherical = sky_spherical_coordinates(dir);
float theta = spherical[0];
float phi = spherical[1];
sunsky.theta = theta;
sunsky.phi = phi;
sunsky.dir = dir;
float theta2 = theta * theta;
float theta3 = theta2 * theta;
float T = turbidity;
float T2 = T * T;
float chi = (4.0 / 9.0 - T / 120.0) * (M_PI - 2.0 * theta);
sunsky.zenith_Y = (4.0453 * T - 4.9710) * tan(chi) - 0.2155 * T + 2.4192;
sunsky.zenith_Y *= 0.06;
sunsky.zenith_x =
( 0.00166 * theta3 - 0.00375 * theta2 + 0.00209 * theta) * T2 +
(-0.02903 * theta3 + 0.06377 * theta2 - 0.03202 * theta + 0.00394) * T +
( 0.11693 * theta3 - 0.21196 * theta2 + 0.06052 * theta + 0.25886);
sunsky.zenith_y =
( 0.00275 * theta3 - 0.00610 * theta2 + 0.00317 * theta) * T2 +
(-0.04214 * theta3 + 0.08970 * theta2 - 0.04153 * theta + 0.00516) * T +
( 0.15346 * theta3 - 0.26756 * theta2 + 0.06670 * theta + 0.26688);
sunsky.perez_Y[0] = ( 0.1787 * T - 1.4630);
sunsky.perez_Y[1] = (-0.3554 * T + 0.4275);
sunsky.perez_Y[2] = (-0.0227 * T + 5.3251);
sunsky.perez_Y[3] = ( 0.1206 * T - 2.5771);
sunsky.perez_Y[4] = (-0.0670 * T + 0.3703);
sunsky.perez_x[0] = (-0.0193 * T - 0.2592);
sunsky.perez_x[1] = (-0.0665 * T + 0.0008);
sunsky.perez_x[2] = (-0.0004 * T + 0.2125);
sunsky.perez_x[3] = (-0.0641 * T - 0.8989);
sunsky.perez_x[4] = (-0.0033 * T + 0.0452);
sunsky.perez_y[0] = (-0.0167 * T - 0.2608);
sunsky.perez_y[1] = (-0.0950 * T + 0.0092);
sunsky.perez_y[2] = (-0.0079 * T + 0.2102);
sunsky.perez_y[3] = (-0.0441 * T - 1.6537);
sunsky.perez_y[4] = (-0.0109 * T + 0.0529);
sunsky.zenith_Y /= sky_perez_function(sunsky.perez_Y, 0, theta);
sunsky.zenith_x /= sky_perez_function(sunsky.perez_x, 0, theta);
sunsky.zenith_y /= sky_perez_function(sunsky.perez_y, 0, theta);
}
shader node_sky_texture(
int use_mapping = 0,
matrix mapping = matrix(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
vector Vector = P,
vector sun_direction = vector(0, 0, 1),
float turbidity = 2.2,
output color Color = 0.0)
{
vector p = Vector;
if (use_mapping)
p = transform(mapping, p);
KernelSunSky sunsky;
precompute_sunsky(sun_direction, turbidity, sunsky);
Color = sky_xyz_radiance(sunsky, p);
}
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