mx_generalized_schlick_bsdf.osl

#include "lib/mx_microfacet_specular.osl"

void mx_generalized_schlick_bsdf(float weight, color color0, color color90, float exponent, vector2 roughness, normal N, vector U, string distribution, string scatter_mode, output BSDF bsdf)
{
    float avgF0 = dot(color0, color(1.0 / 3.0));
    float ior = mx_f0_to_ior(avgF0);

    if (scatter_mode == "T")
    {
        bsdf.response = weight * microfacet(distribution, N, U, roughness.x, roughness.y, ior, 1);
        bsdf.throughput = weight;
        return;
    }

    float NdotV = fabs(dot(N,-I));
    color F = mx_fresnel_schlick(NdotV, color0, color90, exponent);

    // Calculate compensation for multiple scattering.
    // This should normally be done inside the closure
    // but since vanilla OSL doesen't support this we
    // add it here in shader code instead.
    vector2 safeAlpha = clamp(roughness, M_FLOAT_EPS, 1.0);
    float avgAlpha = mx_average_alpha(safeAlpha);
    color comp = mx_ggx_energy_compensation(NdotV, avgAlpha, F);

    // Calculate throughput from directional albedo.
    color dirAlbedo = mx_ggx_dir_albedo(NdotV, avgAlpha, color0, color90) * comp;
    float avgDirAlbedo = dot(dirAlbedo, color(1.0 / 3.0));
    bsdf.throughput = 1.0 - avgDirAlbedo * weight;

    // Calculate the reflection response, setting IOR to zero to disable internal Fresnel.
    bsdf.response = F * comp * weight * microfacet(distribution, N, U, safeAlpha.x, safeAlpha.y, 0.0, 0);

    if (scatter_mode == "RT")
    {
        bsdf.response += bsdf.throughput * microfacet(distribution, N, U, safeAlpha.x, safeAlpha.y, ior, 1);
    }
}