Segmenting Meshes In Zbrush Mini-Tutorial
Hot on the tails of my last tutorial, here's another one for people to use. It's probably not anything new for many production artists, but I'm sure a lot of people will find this useful. I know I am not the first to figure this out. It has also been posted on the ZBrush Wiki.
This is a mini-tutorial explaining how to segment models in zbrush in order to achieve higher polygon counts on individual sections. This is not exactly new material, and though I figured this out on my own, I know for a fact that I'm not the only one to have done so.
Memory is finite, and sometimes the level of detail of a mesh simply isn't enough to get the forms necessary in a mesh. When subdividing the entire model is not feasible or possible, dividing the model in sections may be a workaround to get more detail. However, deleting geometry within Zbrush by hiding the unnecessary geometry and and pressing "Delete Hidden" in the geometry section of the Tool palette results in smoothing the mesh through all subdivision levels, and many details in the highest subdivision are lost.
Hide everything except the section you wish to extract.
Export this section as an OBJ file as you would normally do. Make sure texture (Txr) is on, and if you have groups within this section, make sure you have the groups (Grp) option active as well.
Step up to the highest subdivision level of your tool, keeping the same selection active.
Export the highest subdivision as a separate file with the same options.
Exit edit mode by pressing the "Edit" button at the top of the interface or pressing the "t" key. Deactivate your tool by selecting any other tool in the tools palette.
Create a new tool by importing the low-resolution mesh you exported from your complete mesh.
Subdivide your mesh to the same level the original was at.
Import the highest subdivision you exported.
You now have a segmented mesh with all of the high-resolution detail!
You cannot sculpt seamlessly across these segment divisions. A possible workaround would be to simply create a displacement map from the segmented mesh and then apply it to the full mesh, but the memory limitations probably will not allow this.
You cannot re-import the segments into the original tool, as ZBrush currently does not allow you to import sections of your tool, only the entire mesh, at any subdivision level. A proposed workaround: export the full tool mesh, and the segmented mesh, and import them both into Maya. Since ZBrush is able to control the vertex order when it subdivides the mesh, Maya should, in theory, be able to use the transfer surface tool in the Polygon menu (option box-> Transfer: Verticies) to transfer the vertex positions from one mesh to another. This has not been tested.