Following some documents on internet, I divide my ray tracing result by PDF. Then it seem the D and G terms disappeared. Only F term is still visible, it looks like Fresnel only.
color = D(wh) * G(wo, wi) * F / (4 * wi.z * wo.z);
pdf = D(wi) * G1(wo) * abs(dot(wo, wi)) / (abs(wo.z) * 4 * dot(wo, wh))
color / pdf looks very similar to F term. That's strange, I don't know what's wrong.
G term. If I divide the result by PDF, it's likely to neutralized the effect of
G. But that's obviously wrong.
So, how to use the PDF in correct way. Do I have the correct form of PDF?