Using red and green channels as normal map and using blue as mask?

[Deathrey (DeathreyCG)]

@Whammy

That works, but I was going to use the blue channel for the mask which means the blue magnitude would have to be derived from the red/green magnitudes. However, I wan’t comfortable with the overhead that would entail in the math. So I just went ahead and added an alpha channel and left the RGB channels alone.

Calculating blue channel from red and green is so cheap nowdays, that you would not want even considering this cost. Adding alpha channel however brings you to a point, where using two textures, one with normal map compression, is actually more favorable.