float3 XYZ2xyY( float3 _XYZ ) { float3 xyY; xyY.z = _XYZ.y; xyY.x = _XYZ.x / (_XYZ.x + _XYZ.y + _XYZ.z); xyY.y = _XYZ.y / (_XYZ.x + _XYZ.y + _XYZ.z); return xyY; }