Isn't that just Half-Lambert that Valve came up with for Half-Life?<p>"To soften the diffuse contribution from local lights, the dot product from the Lambertian model is scaled by ½, add ½ and squared. The result is that this dot product, which normally lies in the range of -1 to +1, is instead in the range of 0 to 1 and has a more pleasing falloff. "<p><a href="https://developer.valvesoftware.com/wiki/Half_Lambert" rel="nofollow">https://developer.valvesoftware.com/wiki/Half_Lambert</a>