czm_RGBToXYZ
Converts an RGB color to CIE Yxy.
The conversion is described in Luminance Transform
Parameters:
| Name | Type | Description | 
|---|---|---|
| rgb | vec3 | The color in RGB. | 
Returns:
	
	
		vec3 
		
		 The color in CIE Yxy.
         
    
    
        Example
vec3 xyz = czm_RGBToXYZ(rgb); xyz.x = max(xyz.x - luminanceThreshold, 0.0); rgb = czm_XYZToRGB(xyz);
