ZBrushCentral

Odd Normal Map and Texture Seam Issue

ZBrush Usage Questions
#1

I have run into an issue which ive yet to find a resolve for with texture boarders/seams on a head model. a friend/coworker of mine posted on another site and descirbed the problem fairly well so im going to quote him: The UV’s are laid out in Maya with the top of the head’s UV’s a seperate shell from the rest of the heads UV’s. Basically what is happening is the normal map that I generate in ZBrush, when it hits the texture boarder from the side of the head to the top of the head, the normal map flips and inverses itself. So if I paint a large bump going up the side of the head to the top of the head crossing the texture boarder the bump reverses and now is a large crevice instead of a bump. I’ve checked and double checked the UV’s on the head, making sure they are oriented correctly and they are.

I’ve also tried duplicating the head mesh, deleting the UV’s from it, exporting that mesh with no UV’s as an .obj and then importing that to ZBrush, applying the GUV tool to create a tiled UV layout, painting the detail in and then generating the normal map. The normal map generates fine and does not show up as being inverted on the mesh where it crosses the UV boarder. I then exported the base morph target out and imported that into Maya with the newly created ZBrush UV’s. The problem I’m facing now, since I use mental ray to render, is that it is attempting to use multiple UV sets with a single mesh isn’t working out too well, as some of you know mental ray for Maya doesn’t always like multiple UV sets.

any and all help would be much appreciated. thanks in advance. cheers, Ricardo
#2

How funny, I’ve come across the same issue today, and began searching to see if anyone found a solution. My normal map reverses across seams. It sounds like your solution takes too much effort, and there has to be an easier way, otherwise if there is no solution that’s a major program flaw.

If I find the answer I’ll let you know and hopefully vise versa.

#3

Its not clear in my mind, could you post some screens?

#4

I did figure out, Normal maps will look more correct with larger UV sections all joined together in the layout view. As well bumps will look like bumps and not indents, if the object is Cylindrically mapped so all UV’s are sitting vertically and horizontally similar. Another words all UV’s run left to right and and are aligned the same, as if you merged all edges.

The wierd seam thing doesn’t seem to be fixable so far. As well it’s always at the UV borders. See attached Seam image.

Attachments

seam.jpg

#5

hello everyone thank you for the replies. here are some screen grabs to better demonstrate the issue. on the heads the far left is the Maya render, the center is the map generated within Zbrush, and right image is what was painted in Zbrush. i have checked the normals on the head and made sure the UV’s arent flipped. let me know if you need any other info to better understand the problem.

[img]http://www.concretepixel.com/posts/UVs.jpg[/img]
#6

bump

Anyone else experienced this issue? I was able to replicate the problem on a seperate system with the same files. This is clearly something we are doing wrong in Zbrush since the seams are clearly visible in zbrush after the maps are generated. I tried several mapping techniques and on all of them the normal map reveresed “dirction” at some point

Any ideas anyone?

Scott Spencer

#7

It is also worth noting that I create a cylinder with a standard cylandrical map and still the normal map flips at the seam! This is bizzare!

Scott

#8

bump

Sorry, but I cant imagine no one else has had this problem : /

Aurick? Any suggestions?

Scott

#9

I’m back again. This problem happens in other programs too, where the NM looks flipped when wrapped around an object and across a seam. In fact if you create your NM from lets say ATI normal mapper, it’s the same thing.

ZB2 is creating the NM correctly, but Maya can’t display it correctly. Maya has a problem with NM’s.

If your creating NM’s for a game, most likely the engine will acomadate for it and view it correctly, even flipped UV’s. That would be up to the engineers to make it so. If this for pre-render I would suggest exporting a displacement/bump map to use, at least untill Maya gets with the program. :slight_smile:

Now this is big. ZB2 creates low quality NM’s, even when the setting are set to optimal there’s still jaggies in the image. You can export your NM from ZB2 as large as you possibly can maybe 4096, then res down in Photoshop with a slight blur. Second choice is to export the object, bring into Maya reexport, and use the ATI NM application. This creates a lot nicer NM image.

Of course if there’s other solutions I would def like to hear them… Hope this helped.

See ya.

http://www.schastudios.com

#10

Hi Neble,

I am not using Maya at the moment. The issue is all in Zbrush as the seams and flipping are apparent as soon as the map is generated. This is not as much a problem when using AUV tiles but we cannot depend on that mapping method. Human readable UVs are desirable in this situation.

I am still waiting still on some kind of answer from Pixologic.

Thanks

Scott

#11

You might be waiting for a while. :slight_smile:

I understand what your getting at. I’ve had problems with flipping etc especially when I didn’t have the UV’s merged to create a continues form. Still in the end the seam at the sides would look flipped. The map would reflect that.

Our engineers are stating though, that this shouldn’t be a problem and the engine will compensate.

#12

Hey everyone

II’ve been having a problem of the same nature except in a place where a seam was avoidable. My normal map was using UWV channel 4 and had a strange seam across it. It turns out the seam is in fact a UVW map seam, but on channel 1. I use Zbrush and I let the displacement UVW use 1 by default.
And since UVW channel 1 was unrelated to any of my normal maps, I never thought to check it…

Anyways, long story short, I just made sure that channel 1 was a useless planar map with no seams, and I just used UVW 2, 3, etc as I needed them.
I unwrapped my channel 1 UVW and loaded it into channel 2 (and made my disp maps reliant on channel 2).

My theory is that normal maps in 3DSMax secretly utilize channel 1 for something sinister… even if you map your normals with another channel.

so just keep channel 1 seam-free (or don’t use it at all) and stick to the other channels as you need them.

I don’t have time tonight (deadline) to test this idea on more complicated geometry (the piece I’m working on it missing a side so it could have seams at the open edges), but I hope it helps someone if they’re experiencing the same flavour of this problem.

Update: I left my displacement UWVs in channel 1, added a displace modifier, then added a UVW map modifier on that to override channel 1 with a planar map and it appears to fix the problem. This way you don’t need to move your disp map UVWs to another channel.

#13

I have run into these seams myself. Make sure you don’t have any inverted UVs. In Max this is easily done by going to “tools->Select Inverted Faces” in the Unwrap Modifier. Unfortunately, I don’t know how to do this in Maya. Well, fixing these inverted UV faces helped fix many of the seams.

Good luck

E.

#14

What kind of video card are you guys using? Im using a mobility radeon x800, I think this may be a video card issue.

Im having the same problem. Tried another computer and I don’t seem to have the same problems.

#15

You do know that you can reverse the bumpiness of normal maps in Photoshop, don`t you? Inverting the red channel and the green channel, so that black becomes white, white becomes black has the desired effect. If you have a problem area of your map, if all else fails you could try this. After the inversions you can select all but the area you wanted to change and history-erase back to the pre-inverted state, which will leave only the problem area inverted.

Cheers,

R