UE4 Hammersley CosineSampleHemisphere数值测试

float2 Hammersley( uint Index, uint NumSamples, uint2 Random )
{
	float E1 = frac( (float)Index / NumSamples + float( Random.x & 0xffff ) / (1<<16) );
	float E2 = float( ReverseBits32(Index) ^ Random.y ) * 2.3283064365386963e-10;
	return float2( E1, E2 );
}

NumSapmles=8, Random=0

Index	0	1	2	3	4	5	6	7
u	0	0.125	0.25	0.375	0.5	0.625	0.75	0.875
v	0	0.5	0.25	0.75	0.125	0.625	0.375	0.875

CosineSampleHemisphere()

Index	0	1	2	3	4	5	6	7
x	1	0.3286	0	-0.2588	-0.8040	-0.3235	0	0.1797
y	0	0.3286	0.7071	0.2588	0	-0.3235	-0.6225	-0.1797
z	0	0.7071	0.5	0.866	0.3535	0.7905	0.6123	0.9354

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 Shader

float3 finalColor = float3(0,0,0);
int i = 0;
float numSamples = NumSamples;
while (i < numSamples)
{
  float2 pdf =  CosineSampleHemisphere(Hammersley( i, numSamples, 0 )).xy;
  float2 a = (uv-0.5)*3;
  float2 b =  pdf;
  float d = sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y)); 
  if(d<CircleSize){finalColor.r+=1.0;}
  i++;
}
return finalColor;

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