66 lines
2.2 KiB
GLSL
66 lines
2.2 KiB
GLSL
// From paper http://graphics.cs.williams.edu/papers/AlchemyHPG11/
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// and improvements here http://graphics.cs.williams.edu/papers/SAOHPG12/
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uniform sampler2D dtex;
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uniform float radius = 1.;
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uniform float k = 1.5;
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uniform float sigma = 1.;
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out float AO;
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const float tau = 7.;
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const float beta = 0.002;
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const float epsilon = .00001;
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#define SAMPLES 16
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const float invSamples = 1. / SAMPLES;
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vec3 getXcYcZc(int x, int y, float zC)
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{
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// We use perspective symetric projection matrix hence P(0,2) = P(1, 2) = 0
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float xC= (2 * (float(x)) / screen.x - 1.) * zC / ProjectionMatrix[0][0];
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float yC= (2 * (float(y)) / screen.y - 1.) * zC / ProjectionMatrix[1][1];
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return vec3(xC, yC, zC);
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}
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void main(void)
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{
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vec2 uv = gl_FragCoord.xy / screen;
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float lineardepth = textureLod(dtex, uv, 0.).x;
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int x = int(gl_FragCoord.x), y = int(gl_FragCoord.y);
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vec3 FragPos = getXcYcZc(x, y, lineardepth);
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// get the normal of current fragment
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vec3 ddx = dFdx(FragPos);
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vec3 ddy = dFdy(FragPos);
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vec3 norm = normalize(cross(ddy, ddx));
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float r = radius / FragPos.z;
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float phi = 3. * (x ^ y) + x * y;
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float bl = 0.0;
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float m = log2(r) + 6 + log2(invSamples);
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float theta = 2. * 3.14 * tau * .5 * invSamples + phi;
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vec2 rotations = vec2(cos(theta), sin(theta)) * screen;
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vec2 offset = vec2(cos(invSamples), sin(invSamples));
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for(int i = 0; i < SAMPLES; ++i) {
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float alpha = (i + .5) * invSamples;
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rotations = vec2(rotations.x * offset.x - rotations.y * offset.y, rotations.x * offset.y + rotations.y * offset.x);
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float h = r * alpha;
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vec2 offset = h * rotations;
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m = m + .5;
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ivec2 ioccluder_uv = ivec2(x, y) + ivec2(offset);
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if (ioccluder_uv.x < 0 || ioccluder_uv.x > screen.x || ioccluder_uv.y < 0 || ioccluder_uv.y > screen.y) continue;
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float LinearoccluderFragmentDepth = textureLod(dtex, vec2(ioccluder_uv) / screen, m).x;
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vec3 OccluderPos = getXcYcZc(ioccluder_uv.x, ioccluder_uv.y, LinearoccluderFragmentDepth);
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vec3 vi = OccluderPos - FragPos;
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bl += max(0, dot(vi, norm) - FragPos.z * beta) / (dot(vi, vi) + epsilon);
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}
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AO = max(pow(1.0 - 2. * sigma * bl * invSamples, k), 0.);
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} |