I hope someone can shed some light on what am I doing wrong when trying to implement Cook-Torrance lighting. I've taken the code from "Advanced lighting and materials book", but unfortunately, it gives the following result (I've marked artifact by red arrow):
You can see how the half of the sphere is "cut" instead of having smooth shade.
My HLSL code is the following:
float4 ApplyCookTorrance(float3 InNormal, float3 InWorld)
{
float3 PixelToEye = normalize(EyePos - InWorld);
float3 HalfVector = normalize(LightVector + PixelToEye);
float NdotH = max(0.0f, dot(InNormal, HalfVector));
float3 RoughnessParams = {0.5f, 0.5f, 0.5f};
//Start the "D" term, use Blinn Gaussian
float Alpha = acos(NdotH);
float C = RoughnessParams.x;
float m = RoughnessParams.y;
float D = C * exp(-(pow(Alpha / m, 2.0f)));
//Start the "G" term
float NdotV = dot(InNormal, PixelToEye);
float VdotH = dot(HalfVector, PixelToEye);
float NdotL = dot(LightVector, InNormal);
float G1 = 2 * NdotH * NdotV / NdotH;
float G2 = 2 * NdotH * NdotL / NdotH;
float G = min(1.0f, max(0.0f, min(G1, G2)));
//Start the fresnel term. Use the approximation from
//http://developer.nvidia.com/docs/IO/3035/ATT/FresnelReflection.pdf
float R0 = RoughnessParams.z;
float F = R0 + (1.0f - R0) * pow(1.0f - NdotL, 5.0);
float4 DiffuseColor = {1.0f, 1.0f, 1.0f, 1.0f};
return DiffuseColor * F * D * G / (NdotL * NdotV);
}
I would really appreciate if someone would check my code and tell what is going wrong. Thanks in advance!
P.S. Eye position, light vector and world matrices are specified correctly as other lighting models I've implemented work just fine. My guess is that the problem is in the math here.
You can see how the half of the sphere is "cut" instead of having smooth shade.
My HLSL code is the following:
