Teejoon
107 lines
3.7 KiB
GLSL
107 lines
3.7 KiB
GLSL
#version 430
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//Number of samples per pixel
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#define NUM_SAMPLES (24)
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//Number of turns around the cirle
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#define NUM_TURNS (7)
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uniform sampler2D ViewSpaceZ;
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uniform vec4 ProjInfo;
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uniform float ProjScale;
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//#define ProjScale 500
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uniform float Radius;
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//#define Radius 1.0f
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uniform float Bias;
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//#define Bias 0.012f
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uniform float IntensityDivR6;
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//#define IntensityDivR6 1
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out vec4 fragmentColor;
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vec3 reconstructVSPosition(vec2 ScreenSpaceCoord, float z){
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return vec3((ScreenSpaceCoord * ProjInfo.xy + ProjInfo.zw) * z, z);
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}
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vec3 getPosition(ivec2 ScreenSpaceCoord) {
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vec3 P;
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P.z = texelFetch(ViewSpaceZ, ScreenSpaceCoord, 0).r;
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//Get the xy view space coordinates and add the z value from ViewSpaceZ buffer.
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return reconstructVSPosition(vec2(ScreenSpaceCoord) + vec2(0.5), P.z);
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}
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vec3 getVSFaceNormal(vec3 ViewSpacePosition) {
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// Get tangets vector for the plane and ViewSpacePositin... don't ask how this functions works. It's pure magic.
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// They do this and it just works... I would guess that they approximate the function of a plane from pixels close to the pixel were on now.
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return normalize(cross(dFdx(ViewSpacePosition), dFdy(ViewSpacePosition)));
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}
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vec3 getSampleViewSpacePos(ivec2 ScreenSpaceCoord, int SampleIndex, float RotationAngle, float ScreenSpaceSampleRadius){
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// Pure Magic...
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float alpha = float(SampleIndex + 0.5) * (1.0 / NUM_SAMPLES);
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// Angle to where to sample
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float angle = alpha * (NUM_TURNS * 6.28) + RotationAngle;
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//Lenght to were to sample
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ScreenSpaceSampleRadius = ScreenSpaceSampleRadius * alpha;
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vec2 screenSpaceSampleOffsetVecor = vec2(cos(angle), sin(angle));
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// Get texel coordinate on where to sample by going screenSpaceSampleOffsetVecor direction in ScreenSpaceSampleRadius units from ScreenSpaceCoord (the point being shaded);
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ivec2 screenSpaceSampleTexel = ivec2(ScreenSpaceSampleRadius * screenSpaceSampleOffsetVecor) + ScreenSpaceCoord;
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return getPosition(screenSpaceSampleTexel);
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}
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float Radius2 = Radius * Radius;
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float sampleAO(ivec2 ScreenSpaceCoord, vec3 ShadedViewSpacePosition, vec3 ViewSpaceNormal, float ScreenSpaceSampleRadius, int SampleIndex, float RotationAngle) {
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vec3 sampleViewSpacePosition = getSampleViewSpacePos(ScreenSpaceCoord, SampleIndex, RotationAngle, ScreenSpaceSampleRadius);
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vec3 sampleVector = ShadedViewSpacePosition - sampleViewSpacePosition;
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// vv = sampleVectorLenght ^ 2
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float vv = dot(sampleVector, sampleVector);
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// vn = angle between sampleVector and Normal
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float vn = dot(sampleVector, ViewSpaceNormal);
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const float epsilon = 0.01f;
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// vv < radius2 if the vector is shorter then the radius;
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// vn - bias, offset the angle to reduse self occlusion.
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// epsilon is here to make divison by 0 impossible.
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return float(vv < Radius2) * max((vn - Bias) / (epsilon + vv), 0.0);
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//float f = max(Radius2 - vv, 0.0);
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//return f * f * f * max((vn - Bias) / (epsilon + vv), 0.0);
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}
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void main() {
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ivec2 originScreenCoord = ivec2(gl_FragCoord.xy);
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vec3 origin = getPosition(originScreenCoord);
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vec3 viewSpaceNormal = getVSFaceNormal(origin);
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float screenSpaceSampleRadius = ProjScale * Radius / origin.z;
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//Offset on what angle to start on so that not evry pixel start sampling in the same direction, AlchemyAO
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float rotationAngleOffset = (3 * originScreenCoord.x ^ originScreenCoord.y + originScreenCoord.x * originScreenCoord.y) * 10;
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float sum = 0.0;
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for (int i = 0; i < NUM_SAMPLES; i++) {
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sum += sampleAO(originScreenCoord, origin, viewSpaceNormal, screenSpaceSampleRadius, i, rotationAngleOffset);
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}
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float A = max(0.0, 1.0 - sum * (2.0f / NUM_SAMPLES));
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//fragmentColor= vec4(viewSpaceNormal, 1.0f);
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fragmentColor = vec4(A, A, A, 1.0f);
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}
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