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