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https://github.com/UberGames/lilium-voyager.git
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86 lines
2.5 KiB
GLSL
86 lines
2.5 KiB
GLSL
uniform sampler2D u_ScreenDepthMap;
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uniform vec4 u_ViewInfo; // zfar / znear, zfar
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varying vec2 var_ScreenTex;
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vec2 poissonDisc[9] = vec2[9](
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vec2(-0.7055767, 0.196515), vec2(0.3524343, -0.7791386),
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vec2(0.2391056, 0.9189604), vec2(-0.07580382, -0.09224417),
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vec2(0.5784913, -0.002528916), vec2(0.192888, 0.4064181),
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vec2(-0.6335801, -0.5247476), vec2(-0.5579782, 0.7491854),
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vec2(0.7320465, 0.6317794)
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);
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// Input: It uses texture coords as the random number seed.
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// Output: Random number: [0,1), that is between 0.0 and 0.999999... inclusive.
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// Author: Michael Pohoreski
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// Copyright: Copyleft 2012 :-)
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// Source: http://stackoverflow.com/questions/5149544/can-i-generate-a-random-number-inside-a-pixel-shader
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float random( const vec2 p )
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{
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// We need irrationals for pseudo randomness.
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// Most (all?) known transcendental numbers will (generally) work.
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const vec2 r = vec2(
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23.1406926327792690, // e^pi (Gelfond's constant)
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2.6651441426902251); // 2^sqrt(2) (Gelfond-Schneider constant)
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//return fract( cos( mod( 123456789., 1e-7 + 256. * dot(p,r) ) ) );
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return mod( 123456789., 1e-7 + 256. * dot(p,r) );
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}
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mat2 randomRotation( const vec2 p )
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{
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float r = random(p);
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float sinr = sin(r);
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float cosr = cos(r);
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return mat2(cosr, sinr, -sinr, cosr);
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}
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float getLinearDepth(sampler2D depthMap, const vec2 tex, const float zFarDivZNear)
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{
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float sampleZDivW = texture2D(depthMap, tex).r;
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return 1.0 / mix(zFarDivZNear, 1.0, sampleZDivW);
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}
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float ambientOcclusion(sampler2D depthMap, const vec2 tex, const float zFarDivZNear, const float zFar)
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{
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float result = 0;
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float sampleZ = zFar * getLinearDepth(depthMap, tex, zFarDivZNear);
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vec2 expectedSlope = vec2(dFdx(sampleZ), dFdy(sampleZ)) / vec2(dFdx(tex.x), dFdy(tex.y));
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if (length(expectedSlope) > 5000.0)
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return 1.0;
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vec2 offsetScale = vec2(3.0 / sampleZ);
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mat2 rmat = randomRotation(tex);
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int i;
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for (i = 0; i < 3; i++)
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{
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vec2 offset = rmat * poissonDisc[i] * offsetScale;
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float sampleZ2 = zFar * getLinearDepth(depthMap, tex + offset, zFarDivZNear);
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if (abs(sampleZ - sampleZ2) > 20.0)
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result += 1.0;
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else
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{
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float expectedZ = sampleZ + dot(expectedSlope, offset);
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result += step(expectedZ - 1.0, sampleZ2);
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}
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}
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result *= 0.33333;
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return result;
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}
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void main()
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{
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float result = ambientOcclusion(u_ScreenDepthMap, var_ScreenTex, u_ViewInfo.x, u_ViewInfo.y);
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gl_FragColor = vec4(vec3(result), 1.0);
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}
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