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@alaingalvan
Last active December 27, 2023 20:53
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GPU Pro 3 sample of bent cones screen space ambient occlusion.
void main()
{
vec3 positionX = backproject(depthTexture(pixelCoordinateI), inverseViewProjectionMatrix);
vec3 normalX = normalTexture(pixelCoordinateI);
// get ONB to transform samples
mat3 orthoNormalBasis = computeONB(normalX);
// select samples for pixel out of pattern
int patternOffset = getPatternOffset(pixelCoordinateI);
float ao = 0.0;
int validAODirectionCount = 0;
vec3 bentNormal = vec3(0.0);
float unocclutedDirections = 0.0;
for (int index = 0; index < sampleCount; ++index)
{
vec3 sampleDirection = orthoNormalBasis * getSampleDirection(index, patternOffset);
bool isOutlier = false;
// use float instead of bool and
// apply a fall off function to get smooth AO
float visibility = 1.0;
// this function tests for occlusion in SS
// depending on the actual technique
// and sample distribution
// the implementation of this function varies
checkSSVisibilityWithRayMarchingSmooth(
sampleDirection, maxOccluderDistance,
depthTexture, inverseViewProjectionMatrix,
positionX, normalX,
rayMarchingSteps, rayMarchingStartOffset
visibility, isOutlier);
// we have insufficient information in SS
// here we simply ignore samples
// which can't be handled properly
if (!isOutlier)
{
validAODirectionCount++;
ao += visibility;
}
// for bent normals, we assume,
// that outlier occluders are NOT real occluders!
// sum up unoccluded directions
// direction may be partially visibile
// => only counts accordingly
bentNormal += normalize(sampleDirection) * visibility;
unoccludedDirections += visibility;
}
ao /= float(validAODirectionCount);
bentNormal /= unoccludedDirections;
}
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