import { transformedNormalView } from '../../accessors/Normal.js';
import { positionViewDirection } from '../../accessors/Position.js';
import { sheen, sheenRoughness } from '../../core/PropertyNode.js';
import { Fn, float } from '../../tsl/TSLBase.js';
// https://github.com/google/filament/blob/master/shaders/src/brdf.fs
const D_Charlie = /*@__PURE__*/ Fn( ( { roughness, dotNH } ) => {
const alpha = roughness.pow2();
// Estevez and Kulla 2017, "Production Friendly Microfacet Sheen BRDF"
const invAlpha = float( 1.0 ).div( alpha );
const cos2h = dotNH.pow2();
const sin2h = cos2h.oneMinus().max( 0.0078125 ); // 2^(-14/2), so sin2h^2 > 0 in fp16
return float( 2.0 ).add( invAlpha ).mul( sin2h.pow( invAlpha.mul( 0.5 ) ) ).div( 2.0 * Math.PI );
} ).setLayout( {
name: 'D_Charlie',
type: 'float',
inputs: [
{ name: 'roughness', type: 'float' },
{ name: 'dotNH', type: 'float' }
]
} );
// https://github.com/google/filament/blob/master/shaders/src/brdf.fs
const V_Neubelt = /*@__PURE__*/ Fn( ( { dotNV, dotNL } ) => {
// Neubelt and Pettineo 2013, "Crafting a Next-gen Material Pipeline for The Order: 1886"
return float( 1.0 ).div( float( 4.0 ).mul( dotNL.add( dotNV ).sub( dotNL.mul( dotNV ) ) ) );
} ).setLayout( {
name: 'V_Neubelt',
type: 'float',
inputs: [
{ name: 'dotNV', type: 'float' },
{ name: 'dotNL', type: 'float' }
]
} );
const BRDF_Sheen = /*@__PURE__*/ Fn( ( { lightDirection } ) => {
const halfDir = lightDirection.add( positionViewDirection ).normalize();
const dotNL = transformedNormalView.dot( lightDirection ).clamp();
const dotNV = transformedNormalView.dot( positionViewDirection ).clamp();
const dotNH = transformedNormalView.dot( halfDir ).clamp();
const D = D_Charlie( { roughness: sheenRoughness, dotNH } );
const V = V_Neubelt( { dotNV, dotNL } );
return sheen.mul( D ).mul( V );
} );
export default BRDF_Sheen;