three/src/nodes/functions/BSDF/D_GGX.js

JavaScript 3D library

import { Fn } from '../../tsl/TSLBase.js';

// Microfacet Models for Refraction through Rough Surfaces - equation (33)
// http://graphicrants.blogspot.com/2013/08/specular-brdf-reference.html
// alpha is "roughness squared" in Disney’s reparameterization
const D_GGX = /*@__PURE__*/ Fn( ( { alpha, dotNH } ) => {

	const a2 = alpha.pow2();

	const denom = dotNH.pow2().mul( a2.oneMinus() ).oneMinus(); // avoid alpha = 0 with dotNH = 1

	return a2.div( denom.pow2() ).mul( 1 / Math.PI );

}, { alpha: 'float', dotNH: 'float', return: 'float' } ); // validated

export default D_GGX;