Green bump maps

[gutekfiutek]

Hi.
Anyone knows how it works? And how I can make one? And is it worth doing?
Only thing I can find is:

BTW, in case anyone is confused about why many of the normal maps are now green, its because Armagan is using a common technique of compressing them, where you move the red channel into the alpha channel instead, and drop the blue channel (which you can calculate anyway).  Because of the way DXT compression works, it gives you a higher quality normal map, with fewer compression artefact's (which can be very noticeable if you just use normal compression).

What's the profit of making it that way?
And what dxt comression is used for this?
Thorgrim wrote that it's common technique, but i've never heard about this.

G.

 

[fedeita]

lol i never heared about green normal maps too, btw do you know if it is possible to add normal maps to items and armours?