ZBrushCentral

altering UVs in Zbrush?

ZBrush Usage Questions
#1

in this thread, http://www.pixolator.com/zbc-bin/ultimatebb.cgi?ubb=get_topic&f=1&t=015376

the uv’s of the head object are connected in many places. they are still very much unlike any that would be generated by pretty much any program i know of other than zbrush still. anyway, i’m wondering if there’s a way to interactively alter the uv’s of an object about to be exported (in this case to have a displacement map mapped onto it) i don’t really know the procedure for setting up uv’s in zbrush. whenever i do it i always get every polygon individually seperated from all the others which creates tons of seams and artifacts when rendered in xsi. the particular object i’m unwrapping (an elephant) isn’t exactly easy to unwrap the normal way. but i’m willing to give it another go. however i’d like to be able to have zbrush automatically do it as it worked so well in the above mentioned thread. i do have a few questions though. if my uv’s are created such that there is distortion, will zbrush realize this and compensate when it generates the displacement map? this seems to be the case in some tests i’ve done, but i’m not sure, so i wanted to check.

ok, to reiterate, for anyone that got lost in my rambling :). i’m wondering how i can alter how the uv’s are generated by zbrush, and how i can tell what the hell it is i’m doing to them when i change settings.

thanks

#2

ZBrush has several 1-click mapping options that are available to you, but does not provide the ability to manually edit your mapping.

To apply a mapping method in ZBrush, you need to create a blank texture, apply it to the model and then click the Tool>Texture>Method-of-your-choice. The mapping will be calculated for the texture size that you have created (which should be a multiple of 2: 256x256, 512x512, 1024x1024, 2048x2048 or 4096x4096). If you have not first created a texture, then ZBrush will assume a texture size of 1024x1024. If you then create your displacement map at a larger size than that, you will most likely get the kinds of seams that you’re experiencing. This is because GUVTiles and especially AUVTiles are precision mapping methods and displacement maps are extremely sensitive to errors. An error of a single pixel can result in seams in the final render.

Regarding your UV distortion: ZBrush works with the exact mapping that is applied to the model. If the mapping has distortion, then the map itself will be distorted. Projection Master goes far to compensate for distortions because you paint what you see and let the computer handle the unwrapping process. But poor UV mapping will always give poor final results with any software. This is why GUVTiles is especially good. It’s the next evolution in mapping and is mathematically as distortion-free as is possible for your model. However, you need to apply the mapping correctly in order to ensure good results.

#3

thanks, i’ve been following the practical guide’s instructions which suggested it doesn’t matter if your original texture and the final displacement vary in resolution. i’ll do another test now to see if your suggestion fixes it. also, when i do a guvtiles unwrap in zbrush and import it into xsi, when applying a checkerboard texture to the object, there is loads of distortion and seams. i’m gonnna assume this is normal and that softimage’s procedurals are just not set up for such an unorthodox texture projection. if i’m to paint my textures onto the model in zbrush, will i have to do anything special? or will zbrush automatically generate a seamless texture?

#4

ok even following those exact instructions i’m still getting seams all over. i’m using a 2048x2048 map, would going to 4096x4096 help? the head demonstration uses only a 2048x2048, however my model has a higher poly count. the displacement mapping seems to work whenever i use any model except the one i’m trying to. i’ve tried making sphere’s with displacement as a test, that’s worked, i’ve tried that head demonstration, with some tweaking it worked perfectly. i don’t understand what’s wrong

#5

Could you post examples? Also, please provide the settings that you are using to generate the displacement map.

You might also find your answer somewhere in this thread

#6

ok, here are some specific examples:


and here’s the uv set created by zbrush:

i should also note that when i set the displacement map as the color information for the model in zbrush, i notice none of thse artifacts, it appears to cover the model perfectly, seamlessly. turning off automatic discontinuity sometimes produces a completely blank render, or it does nothing. i’m really at a loss. if anyone knows what could be causing this problem in xsi or mental ray, i’d really like to hear some suggestions.

#7

hmm, that uv looks horrendous, but maybe zb can handle it’s own generated texture over it… I’d make your own uv though, it’s always the only way to guarantee control and quality

#8

I have a similar problem that many people run into.

Sometimes for whatever reson you forget to properlly uv map your object before you start getting into the little details, couple of hours later you realize that you forgot to layout your UV’s. DAM!!

I can go back to Maya and UV the base model, but how do I transfer the uv’s from the base object to the new detailed object in ZBRUSH.

If anyone can help with this, I will be very greatfull.

I’ve been thinking of going into the binary file and replacing the uv info, if possible.

#9

I suspect that the problem you’re getting has to do with a texture anti-aliasing or MIP mapping setting in your rendering engine. This is very often the cause of artifacts in a rendered displacement map – especially when the color map looks fine.

Regarding alexCarbonero’s question, you can redo the UV’s for your subdivision level 1 model at any time before creating the displacement map. When you are ready to create the map, go to subdivision level 1, import your version of the model with the new UV’s, and then create your map. That’s all there is to it. Note that this ONLY works for displacements; you can’t change a texture map after you’ve started painting it.

#10

SWEET!!! this is awsome, you just saved me a ton of time.

no message, no button clicking, just worked.

LOVE IT.

#11

Hmm, I thought it worked, but as soon as I went up the subdivision levels, my model becomes corrupted. Like the vertex order for making the polygons is all out of wack. Here are some sample images,

My high ress model with bad uv’s
1.jpg

any idea how to fix this?

Attachments

2.jpg

3.jpg

4.jpg

#12

The object you imported into your current 3D Tool has a different vertice order. It is most likely a Maya .obj importer setting that is the cause.

In regards to importing a .obj into maya. "When importing, you need to disable Create Multiple Objects by selecting False in the Import Options box to ensure the vertex order doesn't change." The above is taken from the [zbrush 2.0 combined with Maya 5.0 / Mental Ray](http://www.pixol.com.au/zbrush_maya_tutorial.htm) tutorial by Paul Hourmouzis. In any case, if you import a .obj into an existing 3D Tool you will only experience problems if: 1: The vertice order has changed. 2: The vertice/polygon count does not match the current 3D Tools at the current subd level.
#13

yep that did it.