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