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19 lines
619 B
19 lines
619 B
2 years ago
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import { ShaderNode, add, sub, mul, div, pow2 } from '../../shadernode/ShaderNodeBaseElements.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 = new ShaderNode( ( inputs ) => {
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const { alpha, dotNH } = inputs;
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const a2 = pow2( alpha );
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const denom = add( mul( pow2( dotNH ), sub( a2, 1.0 ) ), 1.0 ); // avoid alpha = 0 with dotNH = 1
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return mul( 1 / Math.PI, div( a2, pow2( denom ) ) );
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} ); // validated
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export default D_GGX;
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