UV Master is a free plugin for Z Brush to make unwrapping UVs easy. Unwrapped UVs can then be used to generate the flat textures used by other applications such as 3d software or game engines. It must be downloaded in earlier versions of ZBrush, but comes preinstalled in newer releases.
For a tutorial on exporting and saving individual textures, please look here.
NB- Generated UVs wont hold for a model if you retopologise or use ZRemesher afterwards. This process should only be used after you have finished topologising your model for it’s intended purpose.
Polypainting on the other hand can be carried out either before or after the Unwrapping process, but again should be done after the topology is finished.
(This tutorial is noted from several ZClassroom videos available on youtube)
Step 1: Generate UVS on a low poly clone.
In the Taskbar, click on ZPlugins > UV Master. You can Dock this palette to the side panels for easier access.
When you work with UV master, you will be working on a clone of your current model, so in the UV Master palette, the first button to click is ‘Work on Clone’. A new model will appear on the scene – a clone of your tool at it’s lowest Subdivision level, and with a white material applied. Note that subtools will not be copied.
At this point, there is nothing to stop you simply clicking ‘Unwrap‘ to create a Default UV. Clicking Flatten will then show the flattened version. Unflatten will revert it back to a 3d sculpt.
Clicking the Check Seams button will show where UV Master created the default seams. As you can see in the image below, the default seams are often not placed in adequate places.
To redraw your seams, click the button that says ‘Enable Control Painting‘. Unlike other software, ZBrush doesnt require you to create exact seams from vertex to vertex. Instead you paint a rough guideline for areas you do and dont want to split, then let Zbrush do the rest.
Underneathe this Button are 3 more – Protect, Attract and Erase. Protect will allow you to paint over areas that you do not want seams to be placed. These areas are Red. Attract will allow you to paint areas Blue where seams Will be placed. Erase can be used to make adjustments to your sections. IN the image below, the face will be left untouched, but a seam will be placed running up the back of the head.
Once you have painted where you want your seams, simply click the Unwrap button again to Re-map the model. Clicking flatten will show you your improved UV map.
Step 2: Copy UV to the high poly original.
These UVs are currently only affecting this cloned tool we created from our original. To transfer them back is fairly simple. Click the Copy UVs button in the UV Master palette.
Next, click back on the original high poly tool in the Tool palette, make sure the correct subtool is selected, then back in UV Master simply click Paste UVs.
Using Polygroups to unwrap.
If your Tool or subtool contains polygroups, it can be separated into separate islands simply by clicking the ‘Polygroup‘ button in the UV master palette before unwrapping. Again, you can paint where you want seams to appear in individual polygroups.
Using Ambient Occlusion to unwrap
A cool feature of UV master is to paint our ‘Attract Seams’ guides based on where ambient occlusion happens. Why is this useful? We often want the seams to be hidden or obscured on parts of the model that aren’t often seen. This just so happens to often coincide with areas hit by ambient occlusion – those parts of a model that light cant reach easily. As well as being less visible, the AO itself will help mask the seams.
To use this feature, with the ‘Enable Control Painting’ button active, simply click the ‘AttactFromAmbientOccl’ button to automatically generate your seam guide. Click unwrap and flatten to see the result.
The flattened UV map above is pretty good and clean. However, the face and ears – the most often seen and most detailed parts of most textures, are tiny, with a lot of space given to less important areas such as the shoulders and cranium. This can be rectified by painting Density Guides onto the mesh before unwrapping. Just like we could paint seam guides, we can paint where we want areas of High density (ie – more important, so more texture space) and low density (less important areas – made smaller in the flattened textures).
With Enable Control Painting active, you can also click on the Density Button – there you can set an amount to multiply or divide teh density by, and paint these regions straight onto the model. The image below shows the face painted with a density of *3 (green) and the back of the head with a density of /2 (blue).
The result of this is that when you unwrap and flatten the image again, much more space is allocated to the face than the less important areas. This demonstration is a bit excessive, with a bit of wrinkling in the forehead and under the chin- which could produce streaks or ugly areas in your textures, so try to avoid tight changes in density.
You can save your seam guides and density guides by clicking the SaveCtrMap button in the UV Master palette. Note that this is not the same as saving your flattened textures – it is only saving the unwrapping guides.
You can therefore make several different guide sets for a particular subtool, then save and load them as necessary.