cocos-creator-template/assets/chunks/lighting-models/default-functions/simple-skin.chunk

  #include <surfaces/data-structures/standard>
  #include <lighting-models/includes/standard>

  #if USE_PREINTEGRATED_SKIN
    uniform sampler2D preIntegratedSkinMap; // engine internal assets
  #endif

  #define CC_SURFACES_LIGHTING_MODIFY_FINAL_RESULT
  void SurfacesLightingModifyFinalResult(inout LightingResult result, in LightingIntermediateData lightingData, in SurfacesMaterialData surfaceData, in LightingMiscData miscData)
  {
  #if CC_SURFACES_LIGHTING_SSS
    float sssIntensity = surfaceData.sssParams.x;
    // curvature needs pre-generating in vertex or texture data, otherwise disable pre-integrated skin
    float sssCurvature = surfaceData.sssParams.y;
    float sssColoration = surfaceData.sssParams.z;

    // update lighting data for diffuse calculations
    LightingIntermediateData lightingData3S = lightingData;
    lightingData3S.N = normalize(FSInput_worldNormal);
    lightingData3S.NoL = dot(lightingData3S.N, lightingData.L);
    lightingData3S.NoL = mix(lightingData.NoL, lightingData3S.NoL, sssIntensity);
    lightingData3S.NoLSat = saturate(lightingData3S.NoL);

    float multiplier = lightingData.distAttenuation * lightingData.angleAttenuation;
    #if USE_PREINTEGRATED_SKIN
      result.directDiffuse = texture(preIntegratedSkinMap, vec2(lightingData3S.NoL * 0.5 + 0.5, sssCurvature)).rgb;
      vec3 color = result.directDiffuse / (EPSILON_LOWP + max(max(result.directDiffuse.r, result.directDiffuse.g), result.directDiffuse.b));
      result.directDiffuse *= pow(color, vec3(sssColoration));
      result.directDiffuse *= miscData.lightColorAndIntensity.rgb * miscData.lightColorAndIntensity.w * DiffuseCoefficient_EnergyConservation;
    #else
      result.directDiffuse = CalculateDirectDiffuse(lightingData3S, miscData.lightColorAndIntensity) * multiplier;
    #endif

    #if !CC_FORWARD_ADD
      result.environmentDiffuse = CalculateEnvironmentDiffuse(lightingData3S, cc_ambientSky.w);
    #endif
  #endif
  }