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// total number of samples at each fragment
#define NUM_SAMPLES {{ numSamples }}
#define NUM_SPIRAL_TURNS {{ numSpiralTurns }}
#define USE_ACTUAL_NORMALS {{ useActualNormals }}
#define VARIATION {{ variation }}
uniform sampler2D sGBuffer;
uniform sampler2D sNoise;
uniform float uFOV;
uniform float uIntensity;
uniform vec2 uNoiseScale;
uniform float uSampleRadiusWS;
uniform float uBias;
// reconstructs view-space unit normal from view-space position
vec3 reconstructNormalVS(vec3 positionVS) {
return normalize (cross (dFdx (positionVS), dFdy (positionVS)));
}
vec3 getPositionVS(vec2 uv) {
float depth = decodeGBufferDepth(sGBuffer, uv, clipFar);
vec2 uv2 = uv * 2.0 - vec2 (1.0 );
vec4 temp = viewProjectionInverseMatrix * vec4 (uv2, - 1.0 , 1.0 );
vec3 cameraFarPlaneWS = (temp / temp.w).xyz;
vec3 cameraToPositionRay = normalize (cameraFarPlaneWS - cameraPositionWorldSpace);
vec3 originWS = cameraToPositionRay * depth + cameraPositionWorldSpace;
vec3 originVS = (viewMatrix * vec4 (originWS, 1.0 )).xyz;
return originVS;
}
// returns a unit vector and a screen-space radius for the tap on a unit disk
// (the caller should scale by the actual disk radius)
vec2 tapLocation(int sampleNumber, float spinAngle, out float radiusSS) {
// radius relative to radiusSS
float alpha = (float (sampleNumber) + 0.5 ) * (1.0 / float (NUM_SAMPLES));
float angle = alpha * (float (NUM_SPIRAL_TURNS) * 6.28 ) + spinAngle;
radiusSS = alpha;
return vec2 (cos (angle), sin (angle));
}
vec3 getOffsetPositionVS(vec2 uv, vec2 unitOffset, float radiusSS) {
uv = uv + radiusSS * unitOffset * (1.0 / viewportResolution);
return getPositionVS(uv);
}
float sampleAO(vec2 uv, vec3 positionVS, vec3 normalVS, float sampleRadiusSS,
int tapIndex, float rotationAngle)
{
const float epsilon = 0.01 ;
float radius2 = uSampleRadiusWS * uSampleRadiusWS;
// offset on the unit disk, spun for this pixel
float radiusSS;
vec2 unitOffset = tapLocation(tapIndex, rotationAngle, radiusSS);
radiusSS *= sampleRadiusSS;
vec3 Q = getOffsetPositionVS(uv, unitOffset, radiusSS);
vec3 v = Q - positionVS;
float vv = dot (v, v);
float vn = dot (v, normalVS) - uBias;
#if VARIATION == 0
// (from the HPG12 paper)
// Note large epsilon to avoid overdarkening within cracks
return float (vv < radius2) * max (vn / (epsilon + vv), 0.0 );
#elif VARIATION == 1 // default / recommended
// Smoother transition to zero (lowers contrast, smoothing out corners). [Recommended]
float f = max (radius2 - vv, 0.0 ) / radius2;
return f * f * f * max (vn / (epsilon + vv), 0.0 );
#elif VARIATION == 2
// Medium contrast (which looks better at high radii), no division. Note that the
// contribution still falls off with radius^2, but we've adjusted the rate in a way that is
// more computationally efficient and happens to be aesthetically pleasing.
float invRadius2 = 1.0 / radius2;
return 4.0 * max (1.0 - vv * invRadius2, 0.0 ) * max (vn, 0.0 );
#else
// Low contrast, no division operation
return 2.0 * float (vv < radius2) * max (vn, 0.0 );
#endif
}
void main() {
vec3 originVS = getPositionVS(vUV);
#if USE_ACTUAL_NORMALS
gBufferGeomComponents gBufferValue = decodeGBufferGeom(sGBuffer, vUV, clipFar);
vec3 normalVS = gBufferValue.normal;
#else
vec3 normalVS = reconstructNormalVS(originVS);
#endif
vec3 sampleNoise = texture2D (sNoise, vUV * uNoiseScale).xyz;
float randomPatternRotationAngle = 2.0 * PI * sampleNoise.x;
float radiusSS = 0.0 ; // radius of influence in screen space
float radiusWS = 0.0 ; // radius of influence in world space
float occlusion = 0.0 ;
// TODO (travis): don't hardcode projScale
float projScale = 40.0 ;// 1.0 / (2.0 * tan(uFOV * 0.5));
radiusWS = uSampleRadiusWS;
radiusSS = projScale * radiusWS / originVS.y;
for (int i = 0 ; i < NUM_SAMPLES; ++ i) {
occlusion += sampleAO(vUV, originVS, normalVS, radiusSS, i,
randomPatternRotationAngle);
}
occlusion = 1.0 - occlusion / (4.0 * float (NUM_SAMPLES));
occlusion = clamp (pow (occlusion, 1.0 + uIntensity), 0.0 , 1.0 );
gl_FragColor = vec4 (occlusion, occlusion, occlusion, 1.0 );
}
Travis Fischer created this gist
Travis Fischer
created
this gist