mirror of
https://github.com/Ttanasart-pt/Pixel-Composer.git
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247 lines
7.5 KiB
GLSL
247 lines
7.5 KiB
GLSL
// Atmospheric Scattering
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// Author: cubi
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// https://www.shadertoy.com/view/XlBfRD
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// License (MIT) Copyright (C) 2017-2018 Rui. All rights reserved.
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#define PI 3.1415926535
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#define PI_2 (3.1415926535 * 2.0)
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#define EPSILON 1e-5
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#define SAMPLES_NUMS 16
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varying vec2 v_vTexcoord;
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varying vec4 v_vColour;
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uniform vec2 dimension;
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uniform int mapping;
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uniform vec2 sunPosition;
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uniform float sunRadius;
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uniform float sunRadiance;
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/*uniform*/ float mieG;
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/*uniform*/ float mieHeight;
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/*uniform*/ float rayleighHeight;
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vec3 waveLambdaMie;
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vec3 waveLambdaOzone;
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vec3 waveLambdaRayleigh;
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float earthRadius;
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float earthAtmTopRadius;
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vec3 earthCenter;
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float saturate(float x) { return clamp(x, 0.0, 1.0); }
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vec3 ComputeSphereNormal(vec2 coord, float phiStart, float phiLength, float thetaStart, float thetaLength) {
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vec3 normal;
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normal.x = -sin(thetaStart + coord.y * thetaLength) * sin(phiStart + coord.x * phiLength);
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normal.y = -cos(thetaStart + coord.y * thetaLength);
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normal.z = -sin(thetaStart + coord.y * thetaLength) * cos(phiStart + coord.x * phiLength);
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return normalize(normal);
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}
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vec2 ComputeRaySphereIntersection(vec3 position, vec3 dir, vec3 center, float radius) {
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vec3 origin = position - center;
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float B = dot(origin, dir);
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float C = dot(origin, origin) - radius * radius;
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float D = B * B - C;
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vec2 minimaxIntersections;
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if (D < 0.0) {
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minimaxIntersections = vec2(-1.0, -1.0);
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} else {
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D = sqrt(D);
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minimaxIntersections = vec2(-B - D, -B + D);
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}
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return minimaxIntersections;
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}
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vec3 ComputeWaveLambdaRayleigh(vec3 lambda) {
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float n = 1.0003;
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float N = 2.545E25;
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float pn = 0.035;
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float n2 = n * n;
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float pi3 = PI * PI * PI;
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float rayleighConst = (8.0 * pi3 * pow(n2 - 1.0, 2.0)) / (3.0 * N) * ((6.0 + 3.0 * pn) / (6.0 - 7.0 * pn));
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return rayleighConst / (lambda * lambda * lambda * lambda);
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}
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float ComputePhaseMie(float theta, float g) {
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float g2 = g * g;
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return (1.0 - g2) / pow(1.0 + g2 - 2.0 * g * saturate(theta), 1.5) / (4.0 * PI);
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}
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float ComputePhaseRayleigh(float theta) {
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float theta2 = theta * theta;
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return (theta2 * 0.75 + 0.75) / (4.0 * PI);
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}
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float ChapmanApproximation(float X, float h, float cosZenith) {
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float c = sqrt(X + h);
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float c_exp_h = c * exp(-h);
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if (cosZenith >= 0.0) {
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return c_exp_h / (c * cosZenith + 1.0);
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} else {
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float x0 = sqrt(1.0 - cosZenith * cosZenith) * (X + h);
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float c0 = sqrt(x0);
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return 2.0 * c0 * exp(X - x0) - c_exp_h / (1.0 - c * cosZenith);
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}
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}
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float GetOpticalDepthSchueler(float h, float H, float earthRadius, float cosZenith) {
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return H * ChapmanApproximation(earthRadius / H, h / H, cosZenith);
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}
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vec3 GetTransmittance(vec3 L, vec3 V) {
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float ch = GetOpticalDepthSchueler(L.y, rayleighHeight, earthRadius, V.y);
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return exp(-(waveLambdaMie + waveLambdaRayleigh) * ch);
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}
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vec2 ComputeOpticalDepth(vec3 samplePoint, vec3 V, vec3 L, float neg) {
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float rl = length(samplePoint);
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float h = rl - earthRadius;
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vec3 r = samplePoint / rl;
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float cos_chi_sun = dot(r, L);
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float cos_chi_ray = dot(r, V * neg);
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float opticalDepthSun = GetOpticalDepthSchueler(h, rayleighHeight, earthRadius, cos_chi_sun);
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float opticalDepthCamera = GetOpticalDepthSchueler(h, rayleighHeight, earthRadius, cos_chi_ray) * neg;
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return vec2(opticalDepthSun, opticalDepthCamera);
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}
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void AerialPerspective(vec3 start, vec3 end, vec3 V, vec3 L, bool infinite, out vec3 transmittance, out vec3 insctrMie, out vec3 insctrRayleigh) {
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float inf_neg = infinite ? 1.0 : -1.0;
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vec3 sampleStep = (end - start) / float(SAMPLES_NUMS);
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vec3 samplePoint = end - sampleStep;
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vec3 sampleLambda = waveLambdaMie + waveLambdaRayleigh + waveLambdaOzone;
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float sampleLength = length(sampleStep);
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vec3 scattering = vec3(0.0);
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vec2 lastOpticalDepth = ComputeOpticalDepth(end, V, L, inf_neg);
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for (int i = 1; i < SAMPLES_NUMS; i++, samplePoint -= sampleStep) {
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vec2 opticalDepth = ComputeOpticalDepth(samplePoint, V, L, inf_neg);
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vec3 segment_s = exp(-sampleLambda * (opticalDepth.x + lastOpticalDepth.x));
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vec3 segment_t = exp(-sampleLambda * (opticalDepth.y - lastOpticalDepth.y));
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transmittance *= segment_t;
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scattering = scattering * segment_t;
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scattering += exp(-(length(samplePoint) - earthRadius) / rayleighHeight) * segment_s;
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lastOpticalDepth = opticalDepth;
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}
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insctrMie = scattering * waveLambdaMie * sampleLength;
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insctrRayleigh = scattering * waveLambdaRayleigh * sampleLength;
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}
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float ComputeSkyboxChapman(vec3 eye, vec3 V, vec3 L, out vec3 transmittance, out vec3 insctrMie, out vec3 insctrRayleigh) {
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bool neg = true;
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vec2 outerIntersections = ComputeRaySphereIntersection(eye, V, earthCenter, earthAtmTopRadius);
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if (outerIntersections.y < 0.0) return 0.0;
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vec2 innerIntersections = ComputeRaySphereIntersection(eye, V, earthCenter, earthRadius);
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if (innerIntersections.x > 0.0) {
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neg = false;
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outerIntersections.y = innerIntersections.x;
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}
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eye -= earthCenter;
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vec3 start = eye + V * max(0.0, outerIntersections.x);
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vec3 end = eye + V * outerIntersections.y;
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AerialPerspective(start, end, V, L, neg, transmittance, insctrMie, insctrRayleigh);
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bool intersectionTest = innerIntersections.x < 0.0 && innerIntersections.y < 0.0;
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return intersectionTest ? 1.0 : 0.0;
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}
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vec4 ComputeSkyInscattering(vec3 eye, vec3 V, vec3 L) {
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vec3 insctrMie = vec3(0.0);
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vec3 insctrRayleigh = vec3(0.0);
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vec3 insctrOpticalLength = vec3(1.0);
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float intersectionTest = ComputeSkyboxChapman(eye, V, L, insctrOpticalLength, insctrMie, insctrRayleigh);
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float phaseTheta = dot(V, L);
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float phaseMie = ComputePhaseMie(phaseTheta, mieG);
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float phaseRayleigh = ComputePhaseRayleigh(phaseTheta);
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float phaseNight = 1.0 - saturate(insctrOpticalLength.x * EPSILON);
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vec3 insctrTotalMie = insctrMie * phaseMie;
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vec3 insctrTotalRayleigh = insctrRayleigh * phaseRayleigh;
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vec3 sky = (insctrTotalMie + insctrTotalRayleigh) * sunRadiance;
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float angle = saturate((1.0 - phaseTheta) * sunRadius);
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float cosAngle = cos(angle * PI * 0.5);
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float edge = ((angle >= 0.9) ? smoothstep(0.9, 1.0, angle) : 0.0);
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vec3 limbDarkening = GetTransmittance(-L, V);
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limbDarkening *= pow(vec3(cosAngle), vec3(0.420, 0.503, 0.652)) * mix(vec3(1.0), vec3(1.2,0.9,0.5), edge) * intersectionTest;
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sky += limbDarkening;
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return vec4(sky, phaseNight * intersectionTest);
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}
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vec3 TonemapACES(vec3 x) {
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float A = 2.51;
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float B = 0.03;
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float C = 2.43;
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float D = 0.59;
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float E = 0.14;
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return (x * (A * x + B)) / (x * (C * x + D) + E);
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}
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float noise(vec2 uv) {
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return fract(dot(sin(uv.xyx * uv.xyy * 1024.0), vec3(341896.483, 891618.637, 602649.7031)));
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}
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void main() {
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vec2 uv = v_vTexcoord;
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vec2 sun = sunPosition / dimension;
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uv.y = 1. - uv.y;
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sun.y = 1. - sun.y;
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vec3 V = ComputeSphereNormal(uv, 0.0, PI_2, 0.0, PI);
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vec3 L = ComputeSphereNormal(vec2(sun.x, sun.y), 0.0, PI_2, 0.0, PI);
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mieG = 0.76;
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mieHeight = 1200.0;
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rayleighHeight = 8000.0;
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earthRadius = 6360000.0;
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earthAtmTopRadius = 6420000.0;
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earthCenter = vec3(0, -earthRadius, 0);
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waveLambdaMie = vec3(2e-7);
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// wavelength with 680nm, 550nm, 450nm
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waveLambdaRayleigh = ComputeWaveLambdaRayleigh(vec3(680e-9, 550e-9, 450e-9));
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// see https://www.shadertoy.com/view/MllBR2
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waveLambdaOzone = vec3(1.36820899679147, 3.31405330400124, 0.13601728252538) * 0.6e-6 * 2.504;
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vec3 eye = vec3(0., 1000.0, 0.);
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vec4 sky = ComputeSkyInscattering(eye, V, L);
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sky.rgb = TonemapACES(sky.rgb * 2.0);
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sky.rgb = pow(sky.rgb, vec3(1.0 / 2.2)); // gamma
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gl_FragColor = vec4(sky.rgb, 1.0);
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}
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