ZBrushCentral

Zbrush UV Map Questions

ZBrush Usage Questions
#1

Hi,

I’ve been using Zbrush for a few months now, and have gotten pretty in depth with it. Now I’m looking to take the rendering aspect further, specifically with the help of Vray/C4D. Though, I’ve been consistently running into the same problems, and I think I just don’t grasp UV’s at all. I’ve done plenty of research, I just can’t seem to wrap my head around it.

  1. I’ve sculpted my model, detailed it, etc. I then “work on clone”, unwrap my UV’s, copy from the lower sub to the higher? Problem is, no matter what I do, I can’t get my UV’s to match up in the external program. I’m essentially wanting to carry over my polypaint, and displacement textures, then overlay a new texture in C4D/Vray. I’m left with seams in the middle, jagged edges, or just nothing. Even when I protect and attract the seams. I’ve also tried just using Decimation master, but as I learned, that will not allow me to add a texture either, evenly, as it’s now triangles. I’ve carried over normals, DM’s, texture maps, but maybe once or twice have they actually worked properly.

  2. On a slightly related note. Posing. Am I supposed to have UVs done before or after I pose the model? Does transposing affect them? Still confused on this, and shockingly, I cannot find a straight answer on it.

I see thousands of people doing this exact process, so I must be missing something huge, because it just does NOT want to work for me. It can’t be that hard to take your low poly, high detailed model into another program to texture/render it. Or perhaps it is. It just feels horrible to spend all that time sculpting, and just be stuck without being able to continue.

Any help would be GREATLY appreciated! Thanks guys

#2

UVs and maps adds a high level of complexity to Zbrush and other programs and it is unavoidable, no single response is going to solve all your problems and you need to do a lot of research.

Think about UVs a as copy of the geometry of the original model sliced and flat, as a skin. The UV points must correspond exactly to the same coded points of geometry. They are numerated and identified individually. They tell to the texture how to fit with the original geometry and these 2d point will morph with the texture to fit the original 3d points. Like this:

http://dibujos.cuidadoinfantil.net/files/2012/09/Recortables-3D-castillos-fortaleza.jpg

In the case of subdivisions is possible to have the UVs for the lower subdivision model and higher subdivisions will be calculated automatically. In general UVs don’t like very high poly meshes without subdivisions. For example it won’t be easy to create UVs of a 5 million model without subdivisions.

In the case if you deform the geometry there is no problem if the deformation is not extreme. In general you can pose the models after the UVs are done.

What you can not do is to change the topology of the model (add or delete faces etc) as this can change the order of the verts and then the relation of UVs and geometry can be broken. The UVs won’t be able to morph in a natural way with the 3d geometry. There are exceptions, special tools and other programs can be more tolerant to this to certain extend but in general this is a source of problems.

#3

Problem is, no matter what I do, I can’t get my UV’s to match up in the external program. I’m essentially wanting to carry over my polypaint, and displacement textures, then overlay a new texture in C4D/Vray. I’m left with seams in the middle, jagged edges, or just nothing. Even when I protect and attract the seams.

I’m reading the problem a few different ways, so without some images to go on I’ll just take a stab at each scenario I’m picturing in my head:

Scenario A. You’re trying to match the UVs on your highpoly sculpt to an existing lowpoly model that already has UVs. If this is the case, then you’re going to be in for a bad time unless the sculpt has identical topology at the lowest subdivision level. Thankfully, the sculpt usually doesn’t require UVs; only the final lowpoly model needs them for this kind of workflow.

You can just load the low poly into a baking program like xNormal, load in the sculpt from zbrush, and then have it bake all the polypaint, normal, displacement, etc info directly to the lowpoly mesh’s UVs.

Scenario B. You just want to take the base subdivision level of your sculpt and put it into another program using the maps that zbrush created for it, but the textures you exported appear very messed up in the other program.

Did you remember to flip the textures vertically? You can do this in an image editor, inside of zbrush prior to exporting, or probably through your renderer’s material system.

Scenario C. The baked textures actually match the UVs perfectly, but you’re seeing seams from something else.

This could be the result of a low edge padding (Tool: UV Map: UV Map Border). It could be the result of a normal map that isn’t synced to your renderer. It could be a few other incorrectly applied material settings in your renderer beyond the realm of zbrush.

Am I supposed to have UVs done before or after I pose the model?

If the model is going to be animated or reposed into several different poses, I would do them before. If it’s just a single, static pose such as a statue, then it probably wouldn’t matter when you do them.