public override double GetValue(double x, double y)
{
// Get random samples:
Vector3[] samples = RandomSamples[MaterialID_];
// read random normal from noise texture:
// From 0-1 range to 0-RandomVectorImageSize, clamp, then (y*xSize)+x
int pixelIndex = (
((int)(y * RandomVectorImageSize) % RandomVectorImageSize) * RandomVectorImageSize +
((int)(x * RandomVectorImageSize) % RandomVectorImageSize)
);
// Get the colour:
Color randNC = RandomVectorsColours[pixelIndex];
Vector3 randN = new Vector3(randNC.r, randNC.g, randNC.b);
// read scene depth/normal
Color viewNormC = Normals.GetColour(x, y);
Vector3 viewNorm = new Vector3(viewNormC.r, viewNormC.g, viewNormC.b);
float depth = (float)Depth.GetValue(x, y);
float scale = SSAOPower / depth;
// accumulated occlusion factor
float occ = 0f;
int sampleCount = samples.Length;
for (int s = 0; s < sampleCount; s++)
{
// Reflect sample direction around a random vector
Vector3 randomDir = Vector3.Reflect(samples[s], randN);
// Make it point to the upper hemisphere
float flip = (Vector3.Dot(viewNorm, randomDir) >= 0f) ? 1f : -1f;
randomDir *= flip;
// Add a bit of normal to reduce self shadowing
randomDir.x += viewNorm.x * 0.3f;
randomDir.y += viewNorm.y * 0.3f;
randomDir.z += viewNorm.z * 0.3f;
float sD = depth - (randomDir.z * Radius);
// Sample depth at offset location:
float sampleD = (float)Depth.GetValue(x + (randomDir.x * scale), y + (randomDir.y * scale));
float zd = (sD - sampleD);
if (zd > MinZ)
{
// Clamp zd such that it's no higher than 1.
if (zd > 1f)
{
zd = 1f;
}
// This sample occludes, contribute to occlusion
occ += (float)System.Math.Pow(1f - zd, AttenuationPower); // + 1.0-saturate(pow(1.0 - zd, 11.0) + zd) + 1.0/(1.0+zd*zd*10); // iq
}
}
return(1f - (occ / (float)sampleCount));
}