question: uv maps and normal maps

tomenjerry

Hey guys,

I have a question about uv maps. Whenever I make a model, I tend to have a lot of overlap in the uvmap for the diffuse. My question is. Is it common to have 2 uvmaps: one for the diffuse and normal created from that diffuse. And another uv that doesn't have any overlap which I can use for lightmaps (in unreal for example) and a normal map for the major forms? (which I either baked from a quick highpoly mesh or a sculpt).

Hope my question is clear enough.

thanks in advance

Tim

Brian "Panda" Choi

All your normal maps SHOULD share the same UV islands as the diffuse on one UVE set.

Your light map should be a seperate UV set and everything shoudld not be ocerlapping.

Yes, you can have 2 UV sets.

Poinball

Ok, its easy to understand . If you overlap your uv for symmetry its ok. But during the bake of your highpoly you just need to put on the side ( out of the uv square ) one of the uv who overlaping. after the bake you can just replace the symmetry uv.

GlenGramling

Yes it's okay to have a separate UV map just for light maps in Unlreal. However... If your using normal maps its always best for you to give all of your UV shells unique UV space, and not over lap any of them. Overlapping them causes the light to react to the normal map the same for all the UV shells sharing the same space. SO you wont get proper reflections of light... Because of this most games like WoW who use mirrored or over lapped UVs for the texture don't use normal maps at all. Hope this helps.

The plane on the left has overlapped UV shells, notice how the reflections are symmetrical. Where as the UVs for the plane on the right are not overlapped and unique for each side.

HitmonInfinity

We made some buildings in Hawken using different UV maps for diffuse and normals. If I remember correctly, the models had three uv maps: diffuse/spec, normal, and light map. You have to set it up in the material editor though. We were using UE3.

The yellow structures were made using that method:

Brian "Panda" Choi

HitmonInfinity wrote: »

We made some buildings in Hawken using different UV maps for diffuse and normals. If I remember correctly, the models had three uv maps: diffuse/spec, normal, and light map. You have to set it up in the material editor though. We were using UE3.

The yellow structures were made using that method:

Wait, why would the Normals be on a seperate UV set?

HitmonInfinity

Brian Panda Choi wrote: »

Wait, why would the Normals be on a seperate UV set?

The diffuse was using tiling textures that were used in a lot of other places. The normal map was unique. This way, you can get unique surface information that's not in the diffuse.

GlenGramling

Brian Panda Choi wrote: »

Wait, why would the Normals be on a seperate UV set?

Because as I said above the normal map UVs should not be overlapped. Putting them in a separate UV space allows you to overlap the color and spec, and not the normal.

tomenjerry

yeah thanks for the reply guys! Thanks Hitmonlfinity I do exactly the same. I overlap the diffuse and spec to save pixels. have overlap with one normal map, but that is for the little details baked from the diffuse. I never had an issue with specular to be honest. I then have a speperate uv without overlap for the normalmap that hasn't got any overlap, which is for the normal map that gives the surface the right lighting (which I baked from a high poly sculpt). making the diffuse not overlap would be a waste of pixels. to be clear I attached an image with uvs, diffuse etc.


http://i.imgur.com/VXkw6i6.png


Thanks for the reply guys!!

dand3d

Hey Tomenjerry.
The only time you need to have normal maps never over lap is when they are object space normals.
Tangent space normal maps are fine to over lap, as long as the detail is the same and you want the pieces to look the same.

tomenjerry

hey dand,

thanks dude.