ZBrushCentral

Smoothed UV

ZBrush Usage Questions
#1

Long time no post. I hope to be able to post some bits and pieces when I’ve got something more to show.

In the meantime, I’m having a bit of problem with the ZBrush smooth UV setting (SUV).

My general the work flow is to make the base mesh in Maya and then import the OBJ file into Zbrush. I select the SUV button before dividing so that the UVs will smooth as I divide the mesh. But on checking the high Rez mesh it was apparent that the UVs hadn’t been smoothed at all. Have I missed something out? All I can think of is that ZB slpits the UVs when the mesh is imported and as such the UVs can’t be smoothed.

Not having smoothed UVs is going to make it tricky further down the pipeline. The general maya settings for displacement maps is to smooth the UVs so that it will be easier to create textures in Photoshop.

Can someone help me out?

Thanks

MX

#2

Have you tried turning on Tool>Displacement>Smooth UV’s prior to creating your displacement map?

#3

Hi Aurick,

Thanks for your reply. Yeah, I use the Smooth UV’s in the Displacement pallet when generating the Disp map. What I was trying to do was to export a higher rez (4th SubD leve) model out of Zbrush so Maya doesn’t need to calculate the displacement map every time I did a render. Just to speed up reviewing how the texturing is going in the final render.

When I welded the UVs back together in Maya (as the get un-welded in the transition) I noticed that UVs weren’t smoothed. If I exported the 2nd SubD level of model into Maya to render the Disp map then the UVs will only smooth from the 2nd level upwards. So the UVs will have a slight distortion in them.

erm… I’m having trouble explaining myself. I take it the Tool>Displacement>Smooth UV’s only effects the generation of the Displacement map but does not change the meshes UVs. Can you let me know how the SUV setting alters the UVs when it comes to geometry itself?

Thanks

MX

#4

The UVs mesh is smoothed with Suv on when you divide.

But sadly, it totally forgets them the moment you go down a subdivision. So if you divide 3 times with Suv on, it’s smoothed, but if you lower the sdiv back to 1, then go back to the highest, it will be as if you never had Suv on.

Even if you save tool just after dividing with Suv, reloading the tool the smooth uvs are gone again.

Pretty much you’ll need to export an obj right after you divide with Suv because many things will cause you to lose it.

I think it’s pretty much broken feature, the Suv button. I mean you can use Zbrush to create normal maps and displacements with smooth uvs, thanks to their separate smooth uv buttons. Then it just seems backwards that a the major feature like Polypaint, that needs to be at the highest subdivision, doesn’t have a smooth UV option when generating a texture. What good is it to have a none smoothed texture when you are doing smoothed displacements?

#5

Hi Timothy,

Thanks for your reply. So my fears that the SUV feature doesn’t do what it’s meant to do is valid. I wasn’t doing something wrong and it’s a bug with Zbrush. Shame really as it just makes things that little bit more tricky.

Hopefully Pixologic have it listed for being fixed in the next update/version.

Cheers again,

MX

#6

I have added this to the list of issues to look at for the next update.

#7

Thanks Aurick,

Glad that this little bug has been noted. I’ll make sure that my workflow doesn’t rely on UVS in the future. I would ask you when the next update is due… but I know I’d be asking something that is not known, even by you. :slight_smile:

MX

#8

isn’t the SUV feature useless for working with external pipelines??

lets say you have a mouth and are sculpting lips, your pipelins forces you to use a morph target and you will have a SD lvl 0 model.
if you export with smoothed uvs, the lip’s edges will not be in the exact same place you wanted them, because the smoothing shifted a little.

but If you turn off the smoothing in your 3d app, and have none switched on in zbrush, all fits well.
or am I missing something?

#9

Hi. It depends on the pipeline. The problem comes at the high poly end not the base mesh end. When displacement is being used the displacement and texture maps are being applied to a highly tessellated mesh at render time and the UV’s of that tessellated mesh have to match the UV’s of the mesh in Zbrush that the maps were extracted from. Mental Ray’s subdivisional approximation applies exponential smoothing to the UV’s as it tessellates such that if you do not smooth the UV’s of the mesh in Zbrush prior to extracting the maps render artifacts are created where the UV’s differ. Where the ‘smooth uv’ button (under ‘displacement’) does the job for displacement maps irrespective of the SUV button (under 'geometry) there is no such equivalent for texture maps. I would bet that the smoothed uv’s are dropped when going from higher to lower subdivisions so as to leave the base mesh uv’s intact but that it is not quite working as intended.

BTW - It seems like you should be able to switch the subdivisional approximation node from exponential to linear uv smoothing which would remove the need to smooth the uv’s in zbrush at all but I haven’t been able to figure out how to do it as yet :evil:

#10

well as for XSI you can do that, and this way you have a perfect sitting texture on all subd levels…

#11

Tkman: please tell more… I am trying to get around smooth UV problem myself. Thanks.

edit - sorry, should have taken a moment and looked myself. Found the tick box to remove smoothing. Thanks.

#12

well the base thing is: smothed uvs adapts the uvlayout to the actual subd level of your object…
If you have lets say lips or an eye and you paint a texture for it, It is depending on your workflow what you use. I am ususally forced to use morph targets in zbrush and a low res mesh as base for paralel scene enhancements while I am zbrushing, or animation is done at the same time.
This is case A, faster, but inaccurate and you will not get the best result from the nice zbrushing…
Case B means: you have the freedom to zbrush, and start texturing AFTER it and you will be able to use subd lvvl 2 or 3 (depending on what you do) as base.

I case A Textures and the maps are calculated based on lowres mesh, meaning if you paint the edge of an eyelid or lip based on an Uv snapshot, you usually use an edge as referense, meaning you will paint a lip that has an somewhat edgy character. If you subdivide this, an uvs are smoothed, the edge of the lips you painted so accurate will wander around, meaning it is shifted somewhat due the smoothing.
turning smooth uvs off (in 3D app) ensures that it tays where you want it.
You could still use smooth uvs and do some guessing and texting with textures, but if the zbrushmaps are not in place, it will easily give artifacts (borders and edges have this nice zebra pattern)

If you are lucky and have case B you can simply work with the smoothed uvs for the final level you use, meaning you can paint a more round lip eyelid or whatever and be happy with it. the worst shifting happens during the first 2 Subdivisions, so if you are working on 2 or 3 and have to go up for some passes, it will not matter that much.

I personally prefer case B, cause who wants to paint edgy textures that ought to be round??

please correct me if I am wrong

#13

but the problem is still the same

and it´s driving ALL OF US nuts

#14

Just wanted to say here, that I´m very frustrated about that fact!

Still no changes in that case. What is the new AO masking and all polypaint use for, if only the Displacement and the Normals smooth the uvs but not the re-imported geometry?

Works with lowpoly characters for games, but not in the production pipeline of mid and highpoly models.

#15

so what is production workflow for most places? painting unsmothhed without shifts or painting smoothed with minor shifts?

#16

I know this was mentioned somewhere before.

Store a morph target at the highest sub level. Go to lowest sub level. Delete higher. Divide your model to the same level as before with smooth uv on. Switch to morph target. Now you can paint your model with smooth uv’s.

#17

if you do it like that it works only until you go down the levels and up again, then the uvs are not smoothed anymore (major inconsistency, this must be a bug, but hasn´t been fixed yet (using zb4 at work here)). All in all this is not to fathom why such an important part of working with zbrush (actually getting the work out of it for use in renderings with the best quality) has been that much neglected. Tho zbrush is lovely when sculpting, it is not much more than a headache when you try to get the work out of it.

#18

i don´t understand, why this issue is still there in zbrush 4… with the new paint layers the problem is even worse as there is no workaround left to keep the layers while deleting the higher subd levels…
please, pixo, help us with this problem!