Function SampleDirectionGGX

SampleFramework11/v1.02/Graphics/Sampling.h:121–137

Returns a random direction for sampling a GGX distribution. Does everything in world space.

// Returns a random direction for sampling a GGX distribution.
// Does everything in world space.
inline Float3 SampleDirectionGGX(const Float3& v, const Float3& n, float roughness,
                                 const Float3x3& tangentToWorld, float u1, float u2)
{
    float theta = std::atan2(roughness * std::sqrt(u1), std::sqrt(1 - u1));
    float phi = 2 * Pi * u2;

    Float3 h;
    h.x = std::sin(theta) * std::cos(phi);
    h.y = std::sin(theta) * std::sin(phi);
    h.z = std::cos(theta);

    h = Float3::Normalize(Float3::Transform(h, tangentToWorld));

    float hDotV = std::abs(Float3::Dot(h, v));
    Float3 sampleDir = 2.0f * hDotV * h - v;
    return Float3::Normalize(sampleDir);
}

// Returns the PDF for a particular GGX sample
inline float GGX_PDF(const Float3& n, const Float3& h, const Float3& v, float roughness)