Importing UV in Zbrush

Abracadaniel

So I have imported a 3d obj and made it into a polymesh3d, I have sub divided and sculpted with the sole purpose of exporting the normal map for details. But when you make and obj with uv map into a polymesh3d, the uvmap map is removed. So my question is: is it possible to reimport the uv map unto the new sculpted model?

musashidan

You don't need to turn an imported .obj into a pm3d. It is already one. You only ever need to turn ZB primitives into pm3d.

Yes, you can reimport the uvs. Just import the .obj whilst the tool is active(in edit mode) it will automatically propogate the uvs.

Abracadaniel

musashidan said:

You don't need to turn an imported .obj into a pm3d. It is already one. You only ever need to turn ZB primitives into pm3d.

Yes, you can reimport the uvs. Just import the .obj whilst the tool is active(in edit mode) it will automatically propogate the uvs.

Then it begins to project the whole thing and the result is filled with holes.

musashidan

You can also copy/paste uvs using uvmaster. Can you post some images?

cryrid

Like musashidan said, you won't have to convert the model to a polymesh3d since it already is one. Just import the obj and start sculpting. 

Normally you can just import the same mesh to update UVs or vertex positions. Zbrush does this automatically to the point where it doesn't even tell you. However, this only works when the vertex order is the exact same. If you take any actions that would change the vertex order around, then you now have a completely different mesh. It may appear identical to human eyes, but its a completely different set of data that the computer is seeing. Clicking on the makepolymesh3d button is the kind of thing that would probably change the entire vertex order around. Vertex#5 might be the ear on your original model, but the toe on the model in zbrush. As a result, you wont be able to merely import the old UVs on top, nor will you be able to copy and paste them with UV Master (as that too requires the same vertex order). If you see any kind of pop-up message about Projecting when you import an obj on top of a tool, it means the vertex order does not match up. 

Solution One: You don't need UVs on the sculpt. 

• If you bake your maps outside of zbrush (which you should be doing anyway), then only the lowpoly model needs to have UVs. Your highpoly sculpt won't require UVs. 
  
  

Solution Two: Don't try to transfer the UVs to the sculpt, transfer the sculpt to the UV'd model

• Import your original model as a new subtool, and use Tool: Subtool: Project All to transfer the sculpted/painted detail from the sculpt to this mesh. It might work best to project, subdivide, project, subdivide, and repeat until the mesh contains all the detail. 
  
  

Solution Three: Use an external program to transfer UVs

• Zbrush relies on Vertex Order, but other standard 3d apps can transfer UVs based on other factor such as the closest vertex. You could export the lowest subdivision level of the sculpt (turn polygroup export off, or export it as a single polygroup), use such an external program to transfer the original UVs to it, and then import that back into zbrush. The vertex order should be the same, so it should automatically import the new UVs without telling you. 

thaylan

I've been trying to import UVs from Blender 2.8, and now it worked. All i needed to do was to check "keep vertex order", when importing and exporting with Blender. I did not know this was important, thank you so much guys!