ZBrush to Maya - Normal Map Seams Due to UV Layout

[Dreamdealer2099]

Hey!
I've got to say that i used to have the same problems.The only remedy that i found back then was to work on a map in photoshop to make it more or less seamless.Works fine with displacement maps as well.But i'm sure there must be more rational and easy way to make it.So i would like to hear what other ppl think about it.

[BRASH]

To confirm, displacement maps are working fine on my own UV layout.

http://img7.imageshack.us/my.php?image=nightdisplaceworking.jpghttp://img7.imageshack.us/img7/6891/nightdisplaceworking.jpg

Still no luck with normal maps, which would help accentuate the finer details. I'll keep trying, but if someone else out there has the answer...

EDIT: Here is a link to an old post with the same issue. (http://forums.cgsociety.org/showthread.php?f=140&t=204941&page=1&pp=15) And Link 2. (http://www.highend3d.com/boards/index.php?showtopic=216009) It seems the only way to fix the problem is to hide the UV map borders or make it one, solid UV map.
(http://forums.cgsociety.org/showthread.php?f=140&t=204941&page=1&pp=15)

[BRASH]

I just read a comment posted at the foot of this thread (http://forums.cgsociety.org/showthread.php?t=466180), and it appears this problem has been ongoing for a long time, and no one has a perfect answer.

I've just moved from weeks of Zbrush normal/displacement map and UV nightmares to the very first time exporting a normal map in Mudbox with a Max UV'd mesh and it worked absolutely perfectly with no seams showing in Max render at all!!

This workflow has been an ongoing problematic saga at ZBcentral for years.Almost daily there are people starting threads in frustration and many others coming up with trial and error workarounds leading to more frustration and confusion.

Mudbox answers this with 3 or 4 clicks of the mouse.no problems whatsoever(for me at least)
:thumbsup:

I'm going to try mudbox, and report back once I get an answer.

[JonasNoell]

The problem is possibly the following. Maya can handle bumpmaps and normalmaps only if the UV's are not flipped. You can see if your UV's are flipped by going to UV Editor and search for the menue enry "shade UV's". That will shade all your 'correct' UV's blue and all the backfacing ones red. When you flip all the red UV's so that they become blue you shouldn't have any problem whatsoever. By using Mayas automatic mapping it automaticalle flips the UV's in the right direction. That is a Maya specific problem and is only noticable when you do normalmaps or bumpmaps. The bump or normal value becoms inverted in backfacing UV's areas. Max for example has no problem with flipped UV's.

Greetings,
Jonas

[BRASH]

Appreciate the help Jonas, but I've tackled that well in advance. I'm still trying to get a proper export from ZB to MB, but technical roadblocks are cutting me short...

I've noticed this as well:
The normal result in ZMapper looks fine. No seams...
http://img13.imageshack.us/img13/6097/nmnormalzb.jpg

But just looking at the raw normal map in ZMapper:
http://img9.imageshack.us/img9/7876/nmnormaltexzb.jpg

You can clearly notice the seam. I've viewed tons of tutorials, gone through plenty of FAQ, googled the far corners of the web, and I can't find an answer to something that should not be this complicated.

[BRASH]

OK boys and girls,

I've talked with Scott Spencer on this matter, and to summarize he said this: Normals will always give you trouble. They're never easy to use, but not impossible to work with. You will almost always have seams with normal maps; it's different for all 3D applications and game engines. I tried using Mudbox, but received the same results.

What most artists do is utilize tricks to get around these problems. Usually this involves painting on the RGB channels in Photoshop so that it matches seamlessly with the other UV pieces. Another method is to extract the portion of the geometry where the seam is, make it seamless, then re-export another normal map from ZB, and paint that portion over the original normal map where the seam originally was.

Scott also said that Maya's surface sampler produced the best normal results (if you are working in Maya to begin with), but you were limited to 1 million polygon chunks of your high-res geometry.

Talk about a nightmare... He also said if you can use displacement maps instead of normals, do that. You can use a bump map in conjunction with the displace,instead of normal map, to accentuate details in your model.

If I ever find a perfect solution between ZBrush and Maya, I'll post it in this thread.

[JonasNoell]

I'm sorry but this is wrong. The only time when this problem occurs is when the UV's were backfacing. Since you have no problems with automatic mapping (where you have tons of seams and randomly rotated UV clusters) that is absolutely against you theory. I advise you to check your UV's again, because I have no problem whatsoever with the ZBrush Maya Normalmap workflow...

[BRASH]

I checked again just to satisfy my false hope that something might change, but the maps are all blue. Know this too: I've found that even if I autoUV my model, moving, rotating and scaling all the pieces (all pieces scaled together), the seams will again show up. You have to autoUV, and leave it completely alone.

This is just absolutely galling.

There was a quick test I did where I exported a smoothed cube from Maya to ZB with excellent UVs. Did some quick sculpting, then exported a proper normal map with Maya tangent best settings. On some UV borders, there were no seams, but on the bottom half, there were very visible seams.

One of the solutions Scott mentioned to get additional detail in your model beyond the displacement map is to use bump instead of a normal map.

[JonasNoell]

Hmm ok that is very strange ;) I generally moved away from using normalmaps in maya because as you said the combination of a little displacement and some bumpmapping gave much better and sharper resulats and came much closer to the representation in ZBrush. But I can't remember having any issues like you with normalmaps. I'll look through some older models just to see if I also might just have missed that but I doubt so ;)
Anyway keep us updated!

Greetings,
Jonas

[BRASH]

YO I FIXED IT!

Scott mentioned in our conversation about creating a bump map from a higher subdivision level (3 or 4 - can not exceed 125,000 polys). So, what I did is try to create a normal from a sub level of 3. This will reduce the detail of the normal because the model you're creating it on has carried some of that detail with it, so to counter this, just amp up the sharpness in ZMapper. You can also increase the map's contrast in Photoshop, or push the detail in your ZB model.

http://img16.imageshack.us/img16/5202/nightmarefixed1.jpg

http://img16.imageshack.us/img16/4521/nightmarefixed2.jpg

http://img14.imageshack.us/img14/9945/nightmarefixed3.jpg

The seams are still there, but you have to get really close to see them. This method also creates some faint topology patterns in the normal map, but is hardly something to worry about.

Although I haven't tried using a bump in conjunction with a displacement map yet, my normal map is now fully functional, can be brought directly from ZB to Maya, and looks just fine.

Thanks to those who took the time to help me get this one stomped out. ;]

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