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import { ShaderNode, add, sub, mul, exp2 } from '../../shadernode/ShaderNodeBaseElements.js';
const F_Schlick = new ShaderNode( ( inputs ) => {
const { f0, f90, dotVH } = inputs;
// Original approximation by Christophe Schlick '94
// float fresnel = pow( 1.0 - dotVH, 5.0 );
// Optimized variant (presented by Epic at SIGGRAPH '13)
// https://cdn2.unrealengine.com/Resources/files/2013SiggraphPresentationsNotes-26915738.pdf
const fresnel = exp2( mul( sub( mul( - 5.55473, dotVH ), 6.98316 ), dotVH ) );
return add( mul( f0, sub( 1.0, fresnel ) ), mul( f90, fresnel ) );
} ); // validated
export default F_Schlick;