24 lines
668 B
JavaScript
24 lines
668 B
JavaScript
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import { tslFn } from '../../shadernode/ShaderNode.js';
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// Microfacet Models for Refraction through Rough Surfaces - equation (33)
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// http://graphicrants.blogspot.com/2013/08/specular-brdf-reference.html
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// alpha is "roughness squared" in Disney’s reparameterization
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const D_GGX = tslFn( ( { alpha, dotNH } ) => {
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const a2 = alpha.pow2();
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const denom = dotNH.pow2().mul( a2.oneMinus() ).oneMinus(); // avoid alpha = 0 with dotNH = 1
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return a2.div( denom.pow2() ).mul( 1 / Math.PI );
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} ).setLayout( {
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name: 'D_GGX',
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type: 'float',
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inputs: [
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{ name: 'alpha', type: 'float' },
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{ name: 'dotNH', type: 'float' }
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]
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} ); // validated
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export default D_GGX;
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