You'll notice that the Luminance function we are using will return the dot product between the color passed in and a property called unity_ColorSpaceLuminance. To see what that is, you can use Find menu in your text editor (Ctrl + F) and type it in. After searching for it, you should be able to see the following on line 28:
#ifdef UNITY_COLORSPACE_GAMMA#define unity_ColorSpaceGrey fixed4(0.5, 0.5, 0.5, 0.5)#define unity_ColorSpaceDouble fixed4(2.0, 2.0, 2.0, 2.0)#define unity_ColorSpaceDielectricSpec half4(0.220916301, 0.220916301, 0.220916301, 1.0 - 0.220916301)#define unity_ColorSpaceLuminance half4(0.22, 0.707, 0.071, 0.0) // Legacy: alpha is set to 0.0 to specify gamma mode#else // Linear values#define unity_ColorSpaceGrey ...
