mirror of
https://github.com/OpenSpace/OpenSpace.git
synced 2026-04-28 14:59:31 -05:00
Alexander Bock
80 lines
4.3 KiB
GLSL
80 lines
4.3 KiB
GLSL
/*****************************************************************************************
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* *
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* OpenSpace *
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* *
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* Copyright (c) 2014-2020 *
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* *
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* Permission is hereby granted, free of charge, to any person obtaining a copy of this *
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* software and associated documentation files (the "Software"), to deal in the Software *
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* without restriction, including without limitation the rights to use, copy, modify, *
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* merge, publish, distribute, sublicense, and/or sell copies of the Software, and to *
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* permit persons to whom the Software is furnished to do so, subject to the following *
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* conditions: *
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* *
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* The above copyright notice and this permission notice shall be included in all copies *
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* or substantial portions of the Software. *
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* *
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, *
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* INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A *
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* PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT *
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* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF *
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* CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE *
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* OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. *
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****************************************************************************************/
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#version __CONTEXT__
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#include "atmosphere_common.glsl"
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out vec4 renderTarget1;
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uniform float r;
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uniform vec4 dhdH;
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//uniform sampler2D transmittanceTexture;
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uniform sampler3D deltaJTexture;
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// The integrand here is the f(y) of the trapezoidal rule:
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vec3 integrand(const float r, const float mu, const float muSun, const float nu, const float dist) {
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// We can calculate r_i by the cosine law: r_i^2=dist^2 + r^2 - 2*r*dist*cos(PI-theta)
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float r_i = sqrt(r * r + dist * dist + 2.0f * r * dist * mu);
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// r_i can be found using the dot product:
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// vec(y_i) dot vec(dist) = cos(theta_i) * ||vec(y_i)|| * ||vec(dist)||
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// But vec(y_i) = vec(x) + vec(dist), also: vec(x) dot vec(dist) = cos(theta) = mu
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// So, cos(theta_i) = mu_i = (r*dist**mu + dist*2)/(r_i*dist)
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float mu_i = (r * mu + dist) / r_i;
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// muSun_i can also be found by the dot product:
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// cos(sigma_i) = muSun_i = (vec(s) dot vec(y_i))/(||vec(y_i)|| * ||vec(s)||)
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// But vec(y_i) = vec(x) + vec(dist), and vec(x) dot vec(s) = muSun, cos(sigma_i + theta_i) = nu
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float muSun_i = (r * muSun + dist * nu) / r_i;
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// The irradiance attenuated from point r until y (y-x = dist)
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return transmittance(r, mu, dist) * texture4D(deltaJTexture, r_i, mu_i, muSun_i, nu).rgb;
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}
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vec3 inscatter(float r, float mu, float muSun, float nu) {
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vec3 inScatteringRadiance = vec3(0.0f);
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float dy = rayDistance(r, mu) / float(INSCATTER_INTEGRAL_SAMPLES);
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vec3 inScatteringRadiance_i = integrand(r, mu, muSun, nu, 0.0);
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// In order to solve the integral from equation (11) we use the trapezoidal
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// rule: Integral(f(y)dy)(from a to b) = ((b-a)/2n_steps)*(Sum(f(y_i+1)+f(y_i)))
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// where y_i+1 = y_j
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for (int i = 1; i <= INSCATTER_INTEGRAL_SAMPLES; ++i) {
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float y_j = float(i) * dy;
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vec3 inScatteringRadiance_j = integrand(r, mu, muSun, nu, y_j);
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inScatteringRadiance += (inScatteringRadiance_i + inScatteringRadiance_j) / 2.0 * dy;
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inScatteringRadiance_i = inScatteringRadiance_j;
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}
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return inScatteringRadiance;
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}
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void main(void) {
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float mu = 0.0f, muSunun = 0.0f, nu = 0.0f;
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// Unmapping the variables from texture texels coordinates
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// to mapped coordinates
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unmappingMuMuSunNu(r, dhdH, mu, muSunun, nu);
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// Write to texture deltaSR
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renderTarget1 = vec4(inscatter(r, mu, muSunun, nu), 1.0);
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}
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