vec3 HammonEarlGgxDiffuseApprox(in DisneyMaterial mat, in vec3 wm, in vec3 wo, in vec3 wi)
{
    float NoV = CosTheta(wo);
    float NoL = CosTheta(wi);

    if (NoV <= 0.0 || NoL <= 0.0) return vec3(0);

    float NoH = CosTheta(wm);
    float VoL = dot(wo, wi);

    float alpha = mat.roughness * mat.roughness;

    float facing = 0.5 + 0.5 * VoL;
    float roughy = facing * (0.9 - 0.4 * facing) * (0.5 + NoH)/NoH;
    float smoothy = 1.05 * (1.0 - pow(1.0 - NoL, 5.0)) * (1.0 - pow(1.0 - NoV, 5.0));
    float single = INV_PI * mix(smoothy, roughy, alpha);
    float multi = alpha * 0.1159;
    return mat.albedo * (single + mat.albedo * multi);
}