Mirroring a Normal Map?

kunglao

I have a human figure and i want to just mirror half of her face (saving on texture space).

I had read you cannot mirror normal maps,but recently read somewhere that you could unwrap the head,split into 2,move half of the UV'S out of the 0,1 UV square space,Create your Normal map and then move the Uv's back overlaying the original half.

I tend to create my Normal maps in Zbrush.

Any advice would be greatly appreciated

MoP

Mirroring half the UVs is all you need to do. As you said correctly, move the "mirrored" UVs exactly 1 UV unit out of the UV space (so they are still occupying the same "relative" space as the original UVs, just shifted across one unit).
Then you can bake that.

There's a lot of good information here:
http://wiki.polycount.com/Normal Map

kunglao

Thasnks Mop, nice link.
I did read however that by doing so i would get a seam runnning down the center (which isn't ideal for her face). I did mention off set mirroring-not sure how i implement that (i use 3d max 9 and zb 3.5).

I jus wanted to have half the face/head on one sheet as with my current wip there is a lot of surface detail (pores,creases,etc) that i would like to retain.
I know the result will be symmetrical,that's fine i intend to alter the mesh slightly to uneven that.

MoP

You shouldn't get a seam down the centre if your bake is good and matches the tangent-space of the engine / shader / viewport you're viewing it with.

There seem to be mirroring issues fairly specific to Unreal (UDK) that a lot of people are running into. This is easily avoidable in most cases, and shouldn't happen at all if you're not using UDK.