public Vector3 ImportanceSampleDescretePDF(Vector2 xi, DelegatePDF PDF)
{
float Phi = xi.x;
float CosTheta = xi.y;
// Remap from [-1.0, 1.0] to [0.0 1.0]
float Param = CosTheta * 0.5f + 0.5f;
return(SphericalToCartesian(Phi, SampleDescretePDF(Param)) * PDF(CosTheta));
}
public void PrecomputeDescretePDF(float MinBound, float MaxBound, DelegatePDF PDF)
{
int DescreteCDF_NumSamples = 1 << DescreteCDFNumSamplesPowOf2;
if (DescreteCDF != null && DescreteCDF.Length != DescreteCDF_NumSamples)
{
DescretePDF = null;
DescreteCDF = null;
}
if (DescreteCDF == null)
{
DescretePDF = new float[DescreteCDF_NumSamples];
DescreteCDF = new float[DescreteCDF_NumSamples];
int NumIntervals = DescreteCDF_NumSamples - 1;
float Dx = (MaxBound - MinBound) / (float)NumIntervals;
DescretePDFMinBound = MinBound;
DescretePDFMaxBound = MaxBound;
DescretePDF[0] = PDF(Mathf.Cos(MinBound));
DescreteCDF[0] = 0.0f;
for (int i = 1; i < NumIntervals; ++i)
{
float X = MinBound + Dx * (float)i;
float PdfX = PDF(Mathf.Cos(X));
DescretePDF[i] = PdfX;
DescreteCDF[i] = PdfX * Mathf.Abs(Dx) + DescreteCDF[i - 1];
}
DescretePDF[NumIntervals] = PDF(Mathf.Cos(MaxBound));
DescreteCDF[NumIntervals] = 1.0f;
}
}