Tutorial: ZBrush – All about Tools, Subtools and polygroups.
Every model you sculpt in Zbrush is considered a ‘tool’. When you first open Zbrush, the only thing visible is the Tool column, as shown below:
From here, you can add tools to your canvas, either starting from scratch, from opening a pre-existing one.
‘Load Tool‘ and ‘Save As‘ allow you to load and save tools in progress, such as characters, objects etc. Import and Export allow you to bring in .obj files from other 3d packages, or save them out. Note that when you export, you can choose only the selected subtool as an obj file.
Make PolyMesh3D is an important button to know – when you first load a tool and want to start sculpting, you must click this to make it deformable.
In this image, if you clicked on the large white Polysphere button it would open up a list of premade primitives in ZBrush such as spheres and cubes which are then ready to be sculpted.
Tools such as characters, mechanical objects etc can become complicated and it is often easier to construct them from separate pieces rather than as a single whole. Each piece is known as a subtool, and is managed in the toolbar shown below:
For instance if you had a character, his body could be one subtool, his helmet a different one, his sword another and so on. Only one Subtool can be active at a time, and this is the one that you can sculpt. Simply clicking on another subtool, or using the Up and Down arrows underneath the list will allow another to be selected. The curved arrows allow you to move your selected subtool up and down in the list order, which is important when you want to merge two subtools into one.
You can Rename subtools with the button – since most will start as ‘sphere’ or ‘cube’ this can be handy.
All Low and All High are used to simultaneously adjust the subdivision levels of all subtools. (Subdivision levels have increasing numbers of polys in the sculpt – you can shift between high levels for fine detail sculpting and low levels for adjusting the general shape of your model.)
Duplicate allows you to duplicate an existing subtool, which can then be repositioned.
Append will add a new subtool to the bottom of the list. Insert will put it below the tool you are currently working on. Delete will remove the selected tool from the list.
In the Split Section, you can separate tools into subtools, based on their polygroup settings (see below) . The Merge section does the opposite, allowing you to merge two or more subtools together. Merge down will merge the selected tool into the one directly beneath it, hence why Subtool order is important.
NB: Beside each subtool are several icons. The eye icon toggles visibilty, allowing you to only show certain canvases on screen – handy when working with small parts of detailed models. The first 3 icons represent Additive, Subtractive and Intersection modes, which determine how subtools will interact with each other when merged.
NB: There is a Plugin in the Taskbar called ‘Subtool Master‘ which will allow a few more organisational options when working with your subtools.
Polygroups are a useful way of grouping certain areas of a single subtool, to make selecting and working on them easier. Press Shift + F or press the PolyF button to activate polyframe view, which is like a grid running over the surface of your model.
To make a polygroup, mask off part of your sculpt then press Ctrl + W – it will change colour to signify being part of a new group. Alternatively, open the Polygroup palette and click the Group Masked button. NB: The From Masking button is not recommended as it will not preserve previous polygroups.
Ctrl + Shift + Click on a poly group to hide unselected groups. Do the same again to hide it and show the others. Ctrl + Shift + Click on an empty space to bring back all poly groups.
Depending on your subdivision level, the borders of polygroups can look quite ragged. If you go to the Geometry palette and click the Group Loops button you can smooth the boundaries of your groups. The options nearby will help you refine this smoothing process. NB: This will create a new, very narrow polygroup along the seam.
Split Groups – This option in the Subtool palette will allow you to split a tool into subtools, based on how it is divided into polygroups.
Group Visible: This option will combine all visible polygroups into one.
Since polygroups are created via masks, here are some masking tips:
To mask, hold Ctrl then paint on your model, this will darken the selected area.
To remove polygroups, just mask the whole object and press Ctrl +W to make one single Polygroup again.
To select tight geometry (such as a single finger in a curled fist) Select the move tool, press Ctrl +L Click and drag your mouse over the element you want to mask. This will mask it whilst stopping at the border.
There is a masking palette, with useful options including Grow Mask to make it extend outwrds, Blur Mask and Sharpen Mask to adjust your mask edges.
Deleting geometry is (like everything else) a little bit awkward in ZBrush.
The simplest way is to mask and hide the part of your mesh that you want to delete.
Then in the Geometry Palette, click Modify Topology > Del Hidden. This will delete any geometry that is currently hidden in the current tool.
Note that this will create a hole in your mesh. This can be closed with the Close Holes’ button located in the same tab, but can give triangles or wonky geometry that will need to be fixed later.