//This file is automatically rebuilt by the Cesium build process.
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export default "vec3 lambertianDiffuse(vec3 diffuseColor)\n\
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{\n\
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return diffuseColor / czm_pi;\n\
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}\n\
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\n\
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vec3 fresnelSchlick2(vec3 f0, vec3 f90, float VdotH)\n\
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{\n\
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return f0 + (f90 - f0) * pow(clamp(1.0 - VdotH, 0.0, 1.0), 5.0);\n\
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}\n\
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\n\
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float smithVisibilityG1(float NdotV, float roughness)\n\
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{\n\
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// this is the k value for direct lighting.\n\
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// for image based lighting it will be roughness^2 / 2\n\
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float k = (roughness + 1.0) * (roughness + 1.0) / 8.0;\n\
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return NdotV / (NdotV * (1.0 - k) + k);\n\
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}\n\
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\n\
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float smithVisibilityGGX(float roughness, float NdotL, float NdotV)\n\
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{\n\
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return (\n\
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smithVisibilityG1(NdotL, roughness) *\n\
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smithVisibilityG1(NdotV, roughness)\n\
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);\n\
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}\n\
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\n\
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float GGX(float roughness, float NdotH)\n\
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{\n\
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float roughnessSquared = roughness * roughness;\n\
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float f = (NdotH * roughnessSquared - NdotH) * NdotH + 1.0;\n\
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return roughnessSquared / (czm_pi * f * f);\n\
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}\n\
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\n\
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/**\n\
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* Compute the diffuse and specular contributions using physically based\n\
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* rendering. This function only handles direct lighting.\n\
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* <p>\n\
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* This function only handles the lighting calculations. Metallic/roughness\n\
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* and specular/glossy must be handled separately. See {@czm_pbrMetallicRoughnessMaterial}, {@czm_pbrSpecularGlossinessMaterial} and {@czm_defaultPbrMaterial}\n\
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* </p>\n\
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*\n\
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* @name czm_pbrlighting\n\
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* @glslFunction\n\
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*\n\
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* @param {vec3} positionEC The position of the fragment in eye coordinates\n\
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* @param {vec3} normalEC The surface normal in eye coordinates\n\
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* @param {vec3} lightDirectionEC Unit vector pointing to the light source in eye coordinates.\n\
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* @param {vec3} lightColorHdr radiance of the light source. This is a HDR value.\n\
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* @param {czm_pbrParameters} The computed PBR parameters.\n\
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* @return {vec3} The computed HDR color\n\
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*\n\
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* @example\n\
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* czm_pbrParameters pbrParameters = czm_pbrMetallicRoughnessMaterial(\n\
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* baseColor,\n\
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* metallic,\n\
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* roughness\n\
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* );\n\
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* vec3 color = czm_pbrlighting(\n\
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* positionEC,\n\
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* normalEC,\n\
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* lightDirectionEC,\n\
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* lightColorHdr,\n\
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* pbrParameters);\n\
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*/\n\
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vec3 czm_pbrLighting(\n\
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vec3 positionEC,\n\
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vec3 normalEC,\n\
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vec3 lightDirectionEC,\n\
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vec3 lightColorHdr,\n\
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czm_pbrParameters pbrParameters\n\
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)\n\
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{\n\
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vec3 v = -normalize(positionEC);\n\
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vec3 l = normalize(lightDirectionEC);\n\
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vec3 h = normalize(v + l);\n\
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vec3 n = normalEC;\n\
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float NdotL = clamp(dot(n, l), 0.001, 1.0);\n\
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float NdotV = abs(dot(n, v)) + 0.001;\n\
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float NdotH = clamp(dot(n, h), 0.0, 1.0);\n\
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float LdotH = clamp(dot(l, h), 0.0, 1.0);\n\
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float VdotH = clamp(dot(v, h), 0.0, 1.0);\n\
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\n\
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vec3 f0 = pbrParameters.f0;\n\
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float reflectance = max(max(f0.r, f0.g), f0.b);\n\
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vec3 f90 = vec3(clamp(reflectance * 25.0, 0.0, 1.0));\n\
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vec3 F = fresnelSchlick2(f0, f90, VdotH);\n\
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\n\
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float alpha = pbrParameters.roughness;\n\
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float G = smithVisibilityGGX(alpha, NdotL, NdotV);\n\
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float D = GGX(alpha, NdotH);\n\
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vec3 specularContribution = F * G * D / (4.0 * NdotL * NdotV);\n\
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\n\
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vec3 diffuseColor = pbrParameters.diffuseColor;\n\
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// F here represents the specular contribution\n\
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vec3 diffuseContribution = (1.0 - F) * lambertianDiffuse(diffuseColor);\n\
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\n\
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// Lo = (diffuse + specular) * Li * NdotL\n\
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return (diffuseContribution + specularContribution) * NdotL * lightColorHdr;\n\
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}\n\
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";
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