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/**
* Precomputed Atmospheric Scattering
* Copyright (c) 2008 INRIA
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
/**
* Author: Eric Bruneton
*/
// computes transmittance table T using Eq (5)
#ifdef _VERTEX_
void main() {
gl_Position = gl_Vertex;
}
#else
void getTransmittanceRMu(out float r, out float muS) {
r = gl_FragCoord.y / float(TRANSMITTANCE_H);
muS = gl_FragCoord.x / float(TRANSMITTANCE_W);
#ifdef TRANSMITTANCE_NON_LINEAR
r = Rg + (r * r) * (Rt - Rg);
muS = -0.15 + tan(1.5 * muS) / tan(1.5) * (1.0 + 0.15);
#else
r = Rg + r * (Rt - Rg);
muS = -0.15 + muS * (1.0 + 0.15);
#endif
}
float opticalDepth(float H, float r, float mu) {
float result = 0.0;
float dx = limit(r, mu) / float(TRANSMITTANCE_INTEGRAL_SAMPLES);
float xi = 0.0;
float yi = exp(-(r - Rg) / H);
for (int i = 1; i <= TRANSMITTANCE_INTEGRAL_SAMPLES; ++i) {
float xj = float(i) * dx;
float yj = exp(-(ieeesqrt(r * r + xj * xj + 2.0 * xj * r * mu) - Rg) / H);
result += (yi + yj) / 2.0 * dx;
xi = xj;
yi = yj;
}
return mu < -ieeesqrt(1.0 - (Rg / r) * (Rg / r)) ? 1e9 : result;
}
void main() {
float r, muS;
getTransmittanceRMu(r, muS);
vec3 depth = betaR * opticalDepth(HR, r, muS) + betaMEx * opticalDepth(HM, r, muS);
gl_FragColor = vec4(exp(-depth), 0.0); // Eq (5)
}
#endif
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