mirroring UVs?

zombie420

I see people mirror textures right down the middle pretty often, particularly in faces. I've always assumed this was a huge no-no because some game engines will miscalculate the specular info and create gnarly seams. But as I'm seeing it more and more now, is it a UDK-exclusive issue and most other engines support it just fine?

Eric Chadwick

Yep, many engines do it fine. I've noticed there's often a hairline seam, but mostly it's not too noticeable.

A trick on UDN for fixing the specular seam.
http://udn.epicgames.com/Three/ContentBlog.html#Fixing%20specular%20highlights%20when%20using%20X%20and%20Y%20symmetrical%20texture%20mirroring

One way to avoid it entirely, or at least shift it off-center and thus not so noticeable, is to not mirror down the middle, but offset a few tris. You basically move the UV seam off to the side somewhere, where it's less obvious. Select some UV faces on one side of the seam, detach them, then stitch/weld them to the mirror-edge.

Here's an example by b1ll, where the face mesh was mirrored, then the right side was stitched, to move the mirror-seam off to the left side of the face (the right cheek and ear are used by both sides):
http://img230.imageshack.us/img230/8671/miniskinningtut28hj.jpg

alifarsangi

Eric Chadwick Thanks for ur post, that was useful to me !

but i never had that problem with UDK about mirrored UV maps !
just ensure that one side of mirrored uv map is offseted before baking!

also when u import ur maps to UDK, set ur Compression Sitting to TC_NormalMap, by default UDK sets all ur texture's Compression Sitting to TC_ Default,

and finally for best result in UDK, use Xnormal for making normal maps !