@woosh/meep-engine/src/core/math/physics/brdf/brdf_burley.js

Pure JavaScript game engine. Fully featured and production ready.

import { PI_RECIPROCAL } from "../../PI_RECIPROCAL.js";
import { bsdf_schlick } from "../bsdf/bsdf_schlick.js";


/**
 * @see https://google.github.io/filament/Filament.md.html#listing_diffusebrdf
 * @see Brent Burley. 2012. Physically Based Shading at Disney. Physically Based Shading in Film and Game Production, ACM SIGGRAPH 2012 Courses.
 * N = surface normal
 * L = light direction
 * V = view direction
 * H = normalize( V + L )
 *
 * @param {number} NoV = abs(dot(n, v)) + 1e-5
 * @param {number} NoL = lamp(dot(n, l), 0.0, 1.0)
 * @param {number} LoH = clamp(dot(l, h), 0.0, 1.0)
 * @param {number} roughness surface roughness coefficient
 * @returns {number}
 */
export function brdf_burley(NoV, NoL, LoH, roughness) {
    const f90 = 0.5 + 2.0 * roughness * LoH * LoH;

    const lightScatter = bsdf_schlick(1.0, f90, NoL);
    const viewScatter = bsdf_schlick(1.0, f90, NoV);

    return lightScatter * viewScatter * PI_RECIPROCAL;
}