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import {
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Color,
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ShaderChunk,
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ShaderLib,
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UniformsUtils
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} from 'three';
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/**
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* ------------------------------------------------------------------------------------------
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* Subsurface Scattering shader
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* Based on GDC 2011 – Approximating Translucency for a Fast, Cheap and Convincing Subsurface Scattering Look
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* https://colinbarrebrisebois.com/2011/03/07/gdc-2011-approximating-translucency-for-a-fast-cheap-and-convincing-subsurface-scattering-look/
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*------------------------------------------------------------------------------------------
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*/
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function replaceAll( string, find, replace ) {
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return string.split( find ).join( replace );
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}
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const meshphong_frag_head = ShaderChunk[ 'meshphong_frag' ].slice( 0, ShaderChunk[ 'meshphong_frag' ].indexOf( 'void main() {' ) );
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const meshphong_frag_body = ShaderChunk[ 'meshphong_frag' ].slice( ShaderChunk[ 'meshphong_frag' ].indexOf( 'void main() {' ) );
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const SubsurfaceScatteringShader = {
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name: 'SubsurfaceScatteringShader',
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uniforms: UniformsUtils.merge( [
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ShaderLib[ 'phong' ].uniforms,
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{
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'thicknessMap': { value: null },
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'thicknessColor': { value: new Color( 0xffffff ) },
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'thicknessDistortion': { value: 0.1 },
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'thicknessAmbient': { value: 0.0 },
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'thicknessAttenuation': { value: 0.1 },
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'thicknessPower': { value: 2.0 },
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'thicknessScale': { value: 10.0 }
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}
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] ),
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vertexShader: [
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'#define USE_UV',
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ShaderChunk[ 'meshphong_vert' ],
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].join( '\n' ),
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fragmentShader: [
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'#define USE_UV',
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'#define SUBSURFACE',
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meshphong_frag_head,
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'uniform sampler2D thicknessMap;',
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'uniform float thicknessPower;',
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'uniform float thicknessScale;',
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'uniform float thicknessDistortion;',
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'uniform float thicknessAmbient;',
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'uniform float thicknessAttenuation;',
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'uniform vec3 thicknessColor;',
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'void RE_Direct_Scattering(const in IncidentLight directLight, const in vec2 uv, const in vec3 geometryPosition, const in vec3 geometryNormal, const in vec3 geometryViewDir, const in vec3 geometryClearcoatNormal, inout ReflectedLight reflectedLight) {',
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' vec3 thickness = thicknessColor * texture2D(thicknessMap, uv).r;',
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' vec3 scatteringHalf = normalize(directLight.direction + (geometryNormal * thicknessDistortion));',
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' float scatteringDot = pow(saturate(dot(geometryViewDir, -scatteringHalf)), thicknessPower) * thicknessScale;',
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' vec3 scatteringIllu = (scatteringDot + thicknessAmbient) * thickness;',
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' reflectedLight.directDiffuse += scatteringIllu * thicknessAttenuation * directLight.color;',
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'}',
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meshphong_frag_body.replace( '#include <lights_fragment_begin>',
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replaceAll(
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ShaderChunk[ 'lights_fragment_begin' ],
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'RE_Direct( directLight, geometryPosition, geometryNormal, geometryViewDir, geometryClearcoatNormal, material, reflectedLight );',
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[
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'RE_Direct( directLight, geometryPosition, geometryNormal, geometryViewDir, geometryClearcoatNormal, material, reflectedLight );',
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'#if defined( SUBSURFACE ) && defined( USE_UV )',
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' RE_Direct_Scattering(directLight, vUv, geometryPosition, geometryNormal, geometryViewDir, geometryClearcoatNormal, reflectedLight);',
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'#endif',
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].join( '\n' )
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),
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),
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].join( '\n' ),
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};
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export { SubsurfaceScatteringShader };
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