Annoying lightmap specular seam in UDK

[PogoP]

Hey guys

 

I've had this problem quite a few times before in UDK, but I've never properly used it and this problem has always turned me away from it to be honest, I've never found a proper fix.

 

Basically, I get this nasty seam when I bake my lighting. The model has flipped UVs, but in any other engine that isn't usually a problem. I've read a lot about this particular issue on Polycount etc, but nobody ever seems to have a proper fix for it.

 

Helder/Philip, have you guys ever encountered this? Or anybody else? It's basically whenever you have flipped geo on your models, it causes weird issues on the specular seam, but not in the normal map and diffuse etc.

 

[Pampers]

I think you can either offset the texture coords of the mirrored parts by 1 or disable spec lightmaps in the material iiiiiiiiiiiirc

[PogoP]

Tried offsetting texture coords, it does nothing. Would disabling spec lightmaps make it look rubbish though?

[Pampers]

Found this on polycount

 

UDK uses directional lightmaps, and to compute that directionality UDK has to establish some tangent basis for the surface. The editor does this based on whatever UV's are in channel 0 by default. So, if your doing any kind of texture atlasing or mirroring UV's with normal maps, you can do a little trick. Since your lightmap UV's will always be laid out nice and clean with no overlaps or mirroring, put your lightmap UV's in channel 0 so UDK calculates tangent basis based on those, then your diffuse UV's in channel 1. Then use the coordinate node to set all your UV coordinates to channel 1 in your shaders.

It takes a few extra steps to set up your materials like this but it should fix the issue. Otherwise, stick a mesh in front of it and cover it up

Try that

 

http://www.polycount.com/forum/showthread.php?t=94079

 

http://www.polycount.com/forum/showthread.php?t=98050

Edited January 20, 2014 by Pampers

[PogoP]

Ah yeah I did see that one actually but didn't try it. I know countless people have used UDK and that seems like a bit of a hack to me? Seems a very odd bug to still be getting at this point in it's life!

[Minos]

Does enabling "explicit normals" when importing your FBXs fix the issue? I remember I had a similar problem and managed to get rid of it by using a specific combination of fbx export settings and UDK import settings.

 

Also make sure to use "import" instead of reimport when changing these settings.

[PogoP]

I bow down to your infinite wisdom Minos, thank you so much. That seems (or rather, SEAMS LOL!) to have fixed the issue. Fuck, I just ported everything over to Cryengine as well, in rage.

[TarrySruman]

Is there any reason to have explicit normals off? Is there some benefit to having UDK attempt to figure out the normals instead of just pulling them out of the FBX? Because it does a pretty horrendous job of it and generally ruins everything.

[PogoP]

Yeah seems kinda silly that UDK doesnt have this as the default option. Been tearing my hair out over this and didnt even know that option was there.