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public/sdk/three/jsm/shaders/SubsurfaceScatteringShader.js

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