fixed reverse pathtracing image link and misplaced src files
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# Reverse Path Tracing
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<p align="center">
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<img src="https://git.montehaselino.de/servostar/shadertoy-shaders/src/branch/main/pathtracing/reverse/overview.png"/>
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<img src="https://git.montehaselino.de/servostar/Shadertoy-Shaders/src/branch/main/pathtracing/reverse/overview.png"/>
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</p>
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SDF based ray marching reverse path tracer. Capable of direct and indirect diffuse, specular and refractive ray bounces.
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@ -1,215 +0,0 @@
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const int DEPTH = 32;
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const int AA = 8;
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const vec2 epsilon = vec2(1e-3, 0);
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const float planeNear = 1e-3;
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const float planeFar = 1e2;
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const float fov = 82.0;
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const float PI = 3.141592653589793;
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const float pdf = 2.0 * PI;
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#define UNION(a, b) ((a.x) < (b.x) ? (a) : (b))
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#define SDF vec2
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#define MATERIAL_WHITE 0
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#define MATERIAL_RED 1
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#define MATERIAL_GREEN 2
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#define MATERIAL_BLUE 3
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#define MATERIAL_MIRROR 10
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#define MATERIAL_GLASS 20
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#define MATERIAL_EMISSION 255
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SDF sdfScene(in vec3 pos)
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{
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vec3 q = abs(pos - vec3(0,0.99,-1)) - vec3(0.5, 0.01, 0.5);
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SDF li0 = SDF(length(max(q, 0.0)) + min(max(q.x, max(q.y, q.z)), 0.0), MATERIAL_EMISSION);
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SDF sp1 = SDF(length(pos + vec3( 0.5, 0.5, 1)) - 0.5, MATERIAL_WHITE);
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SDF sp2 = SDF(abs(length(pos + vec3(-0.5, 0.75, 1)) - 0.25) - epsilon[0], MATERIAL_GLASS);
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SDF sp3 = SDF(length(pos + vec3( 0.5,-0.25, 1)) - 0.25, MATERIAL_MIRROR);
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SDF pl0 = SDF( pos.y + 1.0, MATERIAL_WHITE);
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SDF pl1 = SDF(-pos.y + 1.0, MATERIAL_WHITE);
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SDF pl2 = SDF( pos.x + 1.0, MATERIAL_RED);
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SDF pl3 = SDF(-pos.x + 1.0, MATERIAL_GREEN);
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SDF pl4 = SDF(-pos.z, MATERIAL_BLUE);
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SDF pl5 = SDF( pos.z + 4.1, MATERIAL_WHITE);
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SDF box = UNION(pl0, pl1);
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box = UNION(box, pl2);
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box = UNION(box, pl3);
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box = UNION(box, pl4);
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box = UNION(box, pl5);
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box = UNION(box, sp1);
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box = UNION(box, sp2);
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box = UNION(box, sp3);
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return UNION(li0, box);
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}
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vec3 sceneNormal(in vec3 pos)
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{
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return normalize(sdfScene(pos)[0] - vec3(
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sdfScene(pos + epsilon.xyy)[0],
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sdfScene(pos + epsilon.yxy)[0],
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sdfScene(pos + epsilon.yyx)[0]
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));
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}
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// project vector b onto vector a
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vec3 project(in vec3 a, in vec3 b)
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{
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return a * (dot(a, b) / dot(a, a));
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}
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// construct a 3D coordinate system with the input up being the "upwards" facing vector
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// which will be directly stored in w.
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// Mathematically this function will create two non linear vectors of up and generate an orthonormal
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// basis using gram-schmidt.
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// This function assumes "up" being already normalized
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void construct_orthonormal_basis(in vec3 up, out vec3 u, out vec3 v, out vec3 w)
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{
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w = up;
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vec3 n2 = normalize(cross(w, vec3(0, 1.0, 1.0))); // build perpendicular vector from w
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vec3 n3 = cross(w, n2); // create 2nd vector perpendicular to w and n2
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// gram schmidt
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u = n2 - (project(w, n2));
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v = n3 - project(w, n3) - project(u, n3);
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}
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// generate a normalized vector within the bounds of the hemisphere with radius of 1.
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// Z-Coordinate will be "upwards".
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// radius determines the maximum radius the output vector will have.
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// NOTE: shrinkin radius will still result in the output to be normalized
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vec3 cosine_weighted_hemisphere()
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{
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float u1 = random();
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float u2 = random();
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float r = sqrt(u1);
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float theta = 2.0 * PI * u2;
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float x = r * cos(theta);
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float y = r * sin(theta);
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return vec3(x, y, sqrt(1.0 - u1));
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}
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vec3 generate_brdf_ray_direction(in vec3 normal, in vec3 incident) {
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vec3 hemisphere = cosine_weighted_hemisphere();
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vec3 u, v, w;
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construct_orthonormal_basis(normal, u, v, w);
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return u * hemisphere.x + v * hemisphere.y + w * hemisphere.z;
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}
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vec3 tracePath(in vec3 ro, in vec3 rd)
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{
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vec3 col = vec3(0);
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vec3 thr = vec3(1);
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for (int k = 0; k < DEPTH; k++)
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{
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vec3 pos = ro + rd * planeNear;
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float t = planeNear;
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for (int i = 0; i < 256 && t < planeFar; i++)
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{
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SDF h = sdfScene(pos);
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if (h[0] < epsilon[0])
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{
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vec3 nor = sceneNormal(pos);
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switch(int(h[1]))
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{
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case MATERIAL_MIRROR:
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rd = reflect(rd, nor);
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ro = pos - nor * epsilon[0];
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break;
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case MATERIAL_GLASS:
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if (dot(nor, rd) > random())
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{
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rd = refract(rd, -nor, 0.2);
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ro = pos + nor * epsilon[0] * 4.0;
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}
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else
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{
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rd = reflect(rd, nor);
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ro = pos - nor * epsilon[0];
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}
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break;
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default:
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rd = -generate_brdf_ray_direction(nor, rd);
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ro = pos - nor * epsilon[0];
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break;
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}
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float cosTheta = abs(dot(nor, -rd)) * pdf / PI * 0.6667;
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switch(int(h[1]))
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{
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case MATERIAL_EMISSION:
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col += thr * 10.0;
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break;
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case MATERIAL_WHITE:
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thr *= cosTheta;
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break;
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case MATERIAL_RED:
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thr *= vec3(0.9, 0.1, 0.1) * cosTheta;
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break;
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case MATERIAL_GREEN:
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thr *= vec3(0.1, 0.9, 0.1) * cosTheta;
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break;
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case MATERIAL_BLUE:
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thr *= vec3(0.1, 0.1, 0.9) * cosTheta;
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break;
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default:
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break;
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}
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break;
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}
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t += h[0];
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pos += rd * h[0];
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}
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float m = max(thr.x, max(thr.y, thr.z));
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if (random() > m)
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break;
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}
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return col;
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}
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void mainImage(out vec4 fragColor, in vec2 fragCoord)
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{
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SEED = (fragCoord.x * fragCoord.y)/iResolution.y + iTime;
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vec3 col = vec3(0);
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vec3 ro = vec3(0,0,-3.999);
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// take multiple samples per pixel
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// offset each ray direction slightly inside pixel
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// in order to anti aliase
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for (int i = 0; i < AA; i++, SEED++)
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{
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vec2 off = vec2(random(), random()) * 0.5;
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vec2 uv = (fragCoord + off -0.5 * iResolution.xy) / iResolution.y;
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vec3 rd = normalize(vec3(uv, 1.0/tan(fov * 0.008726646259971648)));
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col += tracePath(ro, rd);
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}
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col /= float(AA);
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vec3 prev = texture(iChannel0, fragCoord.xy/iResolution.xy).rgb;
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col = mix(prev, col, 1.0/max(float(iFrame), 1.0));
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fragColor = vec4(col, 1.0);
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}
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@ -1,8 +0,0 @@
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float SEED = 0.0;
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float random()
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{
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SEED ++;
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return fract(cos(SEED) * 2474.0);
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}
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float luminance(vec3 v)
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{
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return dot(v, vec3(0.2126f, 0.7152f, 0.0722f));
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}
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vec3 reinhard_jodie(vec3 v)
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{
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float l = luminance(v);
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vec3 tv = v / (1.0f + v);
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return mix(v / (1.0f + l), tv, tv);
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}
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float tentKernel(in vec2 xy, in float r)
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{
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return (1.0 - abs(xy.x/r)) * (1.0 - abs(xy.y/r)) / (r*r);
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}
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float gaussianWeight(in float delta, in float sigma)
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{
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return exp(-delta*delta/(2.0 * sigma * sigma)) * 2.5 * sigma;
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}
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void mainImage(out vec4 fragColor, in vec2 fragCoord)
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{
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vec2 uv = fragCoord.xy/iResolution.xy;
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vec3 color = texture(iChannel0, uv).rgb;
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fragColor = vec4(reinhard_jodie(color), 1);
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}
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