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UV Groups Only Show as One Group?

ZBrush Usage Questions
#1

Hi zBrushers,

I have tried exporting my obj character from both Max and Maya, and each time it shows up in zBrush as a single polygroup. I checked the UVs in zBrush, and all of the gorups are there (Head, chest, gloves, boots, etc).

I did press the polygroups > Uv Groups, didn’t work, still one group.

I opened it in ZMapper, and pressed Display > 5. UV Seams, and they show up there as well.

This is very frustrating as making selections in zBrush is not a strong point. It would take me an hour to recreate all of those groups that I carefully laid out in Max/Maya.

Somebody please help if you knwo how I might solve this.

Thanks,
Leo

#2

UV Groups can be a bit frustrating at first because different apps tend to define it in different ways.

What ZBrush considers a UV group is a single set of UV coordinates. Let’s take a human, for example, with separate maps for the body and for the head. For ZBrush to see this as two separate groups, one map should use the 0,0 through 1,1 UV space. The other map should use a different UV space such as 1,0 through 2,1 or 0,0 through -1,-1. When your model is set up with multiple UV spaces such as this, ZBrush will recognize each space separately and the UV Groups as well as MD2 features will work as expected.

As you can see, this is quite different from assigning the multiple maps using selection sets (as I believe is done by many users in Max). With selection sets, the maps both use the 0,0 through 1,1 space, but the rendering engine itself is being told to apply different maps based upon the polygon selection. It’s not based off UV coordinates at all.

#3

It sounds like you have misunderstood the meaning of UV Groups.

In Zbrush UV Groups are understood as sets of UV coordinates belonging to the same model but spread across multiple 1 * 1 areas of UV space. For example, the head has its UVs in the 0,0 to 1,1 UV space and the arms has UVs in the 1,0 to 2,1 UV space. Disconnected sets of UVs within a single 1 * 1 area of UV space only add up to 1 UV group in ZBrush, and thus 1 polygroup selection. Spread them across multiple 1 * 1 UV areas and you have UV groups in ZBrush.

If you are only looking for an easy way to select geometry in ZBrush you might try assigning Selection Sets in Maya. These are transfered to the .OBJ format as groups and will be automatically converted to ZBrush’s polygroups upon import. Modo also uses the term Selection Sets that will export to the .OBJ format as groups. I am unaware of any 3DSMax selections/tags/materials that are exported as .OBJ groups.

But remember, if you need to create multiple displacement maps from the same model you still need the UVs spread across multiple 1 * 1 UV areas. If you go that route be sure to keep the various UV sets within 1 * 1 UV areas and do not let a UV span across 2 seperate 1 * 1 UV areas.

EDIT: Awww come on Aurick, I just answered the door and when I return to finish the message you have already replied to this one, and five other threads :smiley: I am sure the shadow under your mouse cursor has trouble keeping up with you.

#4

Very clear explanation, thanks. So for movie characters I can do the multiple maps (as many as needed) on the positive uv grid, but for gaming I can only have 2 color maps, so I’ll use Maya’s selection sets.

Befgore I had tried the 0,0 to 1,1 uv space, but with the head and body as different objects. zBrush made the uvs overlap and so I got frustrated with that method. I suppose I’ll try it again, but with each piece combined as the same object, and then appropriately spread it over the uv space…

Aurick,

You are always so responsive when people are stuck, thanks a lot.

TVeyes,

Since I’m using both Maya and Max, I’ll try using the selection sets in Maya. Just got Modo, and haven’t done any tutorials with it yet, but I here it’s the best for uv unwrapping?

#5

Well, I only use Modo (and ZBrush of course) and have had next to no time for anything CG oriented the last 14-16 months so I am not sure you should be asking me. But I have tried the UV mapping and found it very easy (being an old lightwaver) and quite powerfull. Still, for some things nothings beats a quick ZBrush GUV tiling, works well in the Modo renderer.

#6

Thanks again.

I combined my objects into one, spread the UVs over the postiive grid space (three groups) and then imported, and was able to make automatic poly groups!

Now I just need to get my zBrushed normal map to work in either Maya or Max, and I’m set.

#7

Hello,
im a bit of a newbie… and currently having the same problem as LeoNp…
from what i understood from the replies, i need to move each UV group to a different grid unit… here are screen shots showing what i have…
normal Maya UV layout
attempted Zbrush UV layout
i need to use the same layout in Zbrush as maya’s because i only want to export cavity and displacement maps to Maya
thanks :slight_smile:

#8

Hey Psycho,

Aurick is teh guru, but since you didn’t get a reply yet I’ll try & help. I believe from your screen shots that you are in all 4 quadrant spaces. You should only use the top right (positive x and y) space and then drag each group to the “right” of that space. I still get the UV groups to take a texture map like that in Maya. It is only reading the first square of that quadrant, not the other tow oI have to the right of it. I’m sure there is some setting to make the Hypershader read to the right, but I don’t know how yet. I also don’t know how to load and create texture maps with this whackey layout.

Hope it helps.

Leon

#9

hey there guys, i too am trying to achieve multiple poly groups from my maya mesh into zbrush. is there a mel script that will position all of the uv sets exactly 1 unit away from the 0,0, 1,1, square? thanks a lot.

#10

hmm … it shouldnt be hard to write… if u cant find it anywhere let me know… i might be able to help

#11

Don’t know if you solved your query about the mel script but I though I’d post this as it may be useful for others. The easiest way to move selected uvs exactly one unit in maya is to type the command “polyEditUV -u # -v # ;” in the script editor. So;
Left would be- polyEditUV -u -1 -v 0 ;
Right- polyEditUV -u 1 -v 0 ;
Up- polyEditUV -u 0 -v 1 ;
Down- polyEditUV -u 0 -v -1 ;
I have dragged each of these to the shelf so I have a quick button for each

#12

Hi All… I am a newbie in Zbrush 4 and i am working on a model in Maya and Zbrush
my requirement is that i want to texture my Maya model in Zbrsuh. So i did set up all the UVs in positive UV space in Maya in 6 different UV sets. See the attached image.

uvMaya.jpg
uvMaya.jpg1281×308 116 KB

Now when i import this obj in Zbrush, it show me all the UV sets stacked over each other. Can somebody explain me the steps on how to use this model in zbrush and export different textures for face, arms , body extra.