78 lines
2.4 KiB
Plaintext
78 lines
2.4 KiB
Plaintext
|
|
struct HistogramParameters
|
|
{
|
|
float minLogLum;
|
|
float inverseLogLumRange;
|
|
float timeCoeff;
|
|
uint numPixels;
|
|
Texture2D hdrImage;
|
|
globallycoherent RWStructuredBuffer<uint> histogram;
|
|
RWStructuredBuffer<float> averageLuminance;
|
|
};
|
|
ParameterBlock<HistogramParameters> pHistogramParams;
|
|
|
|
static const float3 RGB_TO_LUMINANCE = float3(0.2125, 0.7154, 0.0721);
|
|
static const float eps = 0.005;
|
|
|
|
uint colorToBin(float3 hdrColor) {
|
|
float lum = dot(hdrColor, RGB_TO_LUMINANCE);
|
|
|
|
if(lum < eps) {
|
|
return 0;
|
|
}
|
|
|
|
float logLum = clamp((log2(lum) - pHistogramParams.minLogLum) * pHistogramParams.inverseLogLumRange, 0, 1);
|
|
|
|
return uint(logLum * 254.0 + 1.0);
|
|
}
|
|
|
|
groupshared uint histogramShared[256];
|
|
|
|
[shader("compute")]
|
|
[numthreads(16, 16, 1)]
|
|
void histogram(uint threadID : SV_GroupIndex, uint2 globalThreadID : SV_DispatchThreadID)
|
|
{
|
|
histogramShared[threadID] = 0;
|
|
GroupMemoryBarrierWithGroupSync();
|
|
|
|
uint2 dim;
|
|
pHistogramParams.hdrImage.GetDimensions(dim.x, dim.y);
|
|
if(globalThreadID.x < dim.x && globalThreadID.y < dim.y) {
|
|
float3 hdrColor = pHistogramParams.hdrImage.Load(int3(globalThreadID, 0)).xyz;
|
|
uint binIndex = colorToBin(hdrColor);
|
|
|
|
InterlockedAdd(histogramShared[binIndex], 1);
|
|
}
|
|
|
|
GroupMemoryBarrierWithGroupSync();
|
|
|
|
InterlockedAdd(pHistogramParams.histogram[threadID], histogramShared[threadID]);
|
|
}
|
|
|
|
[shader("compute")]
|
|
[numthreads(256, 1, 1)]
|
|
void exposure(uint threadID : SV_GroupThreadID)
|
|
{
|
|
uint countForThisBin = pHistogramParams.histogram[threadID];
|
|
histogramShared[threadID] = countForThisBin * threadID;
|
|
|
|
GroupMemoryBarrierWithGroupSync();
|
|
|
|
pHistogramParams.histogram[threadID] = 0;
|
|
|
|
for(uint cutoff = (256 >> 1); cutoff > 0; cutoff >>= 1) {
|
|
if(uint(threadID) < cutoff) {
|
|
histogramShared[threadID] += histogramShared[threadID + cutoff];
|
|
}
|
|
GroupMemoryBarrierWithGroupSync();
|
|
}
|
|
if(threadID == 0) {
|
|
float weightedLogAverage = (histogramShared[0] / max(pHistogramParams.numPixels - float(countForThisBin), 1.0f)) - 1.0f;
|
|
|
|
float weightedAvgLum = exp2(((weightedLogAverage / 254.0f) * pHistogramParams.inverseLogLumRange) + pHistogramParams.minLogLum);
|
|
|
|
float lumLastFrame = pHistogramParams.averageLuminance[0];
|
|
float adaptedLum = lumLastFrame + (weightedAvgLum - lumLastFrame) * pHistogramParams.timeCoeff;
|
|
pHistogramParams.averageLuminance[0] = adaptedLum;
|
|
}
|
|
} |