/**
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* Converts a CIE Yxy color to RGB.
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* <p>The conversion is described in
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* {@link http://content.gpwiki.org/index.php/D3DBook:High-Dynamic_Range_Rendering#Luminance_Transform|Luminance Transform}
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* </p>
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*
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* @name czm_XYZToRGB
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* @glslFunction
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*
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* @param {vec3} Yxy The color in CIE Yxy.
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*
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* @returns {vec3} The color in RGB.
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*
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* @example
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* vec3 xyz = czm_RGBToXYZ(rgb);
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* xyz.x = max(xyz.x - luminanceThreshold, 0.0);
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* rgb = czm_XYZToRGB(xyz);
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*/
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vec3 czm_XYZToRGB(vec3 Yxy)
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{
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const mat3 XYZ2RGB = mat3( 3.2405, -0.9693, 0.0556,
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-1.5371, 1.8760, -0.2040,
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-0.4985, 0.0416, 1.0572);
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vec3 xyz;
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xyz.r = Yxy.r * Yxy.g / Yxy.b;
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xyz.g = Yxy.r;
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xyz.b = Yxy.r * (1.0 - Yxy.g - Yxy.b) / Yxy.b;
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return XYZ2RGB * xyz;
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}
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