306 chapter 9 ■ Normal Maps, Displacement Maps, Maya, and Decimation Master
this button off, each UV would be an unmerged point and could cause problems later
during rendering.) Leave the Scale slider at the default value. It is important not to
change that slider unless you have a specific reason to do so. It is set automatically
by ZBrush. The slider will rescale the object on export, which can be problematic
when you’re trying to render accurate displacements.UVs and Vertex Order
When generating displacement maps in ZBrush, it is important to be sure the UVs do not over-
lap at all. Overlapping UVs (which are easy to miss) will cause unexpected crashes when you
are extracting your displacement map. You can avoid this problem entirely by using ZBrush
Automatic UV (AUV) tiles or other automatic options
for your mapping. This approach will remove any pos-
sibility of overlapping U Vs, but as you will see, hav-
ing UVs laid out in Maya instead will open up several
workflow possibilities not otherwise available. AUV
tiles are not human readable, which makes editing
color maps in Photoshop nearly impossible.
Figure 9.19 is an example of overlapping UVs
in the toes of a model. This problem must be cor-
rected before the displacement map can be extracted.
Otherwise, this small overlap could cause a crash. If at
any point you crash while generating a displacement
map, chances are extremely good that you have a
minor overlapping U V.
Note that unless you are painting color maps
with UV projection techniques, ZBrush is not con-
cerned with UV coordinates This leaves you free to
model and paint in ZBrush and then lay out U Vs later
or change your UV layout without losing all the work
you applied to your model.
ZBrush also offers a tool to check for overlapping UVs under the Tools menu: select
To ol → Texture Map and click the New From UV Check button (Figure 9.20). Clicking this
button will highlight in red on your model any overlapping UVs, so you know where to look
for errors back in Maya. When performing an inspection like this in ZBrush, be sure to
rotate your models to view all surfaces. Figure 9.21 shows the werewolf ZTool with overlap-
ping UVs on the leg noted in red.
You can further check the UVs for exactly where the overlap occurs by clicking the
To ol → Texture Map → Morph UV button (Figure 9.22). This will unfold the mesh in 3D to
its UV shells. Here you can see exactly how the UV shells are overlapping.
This overlapping problem can easily be corrected with the UV Master plug-in. Simply
open ZPlugin → UVMaster and enable Use Existing UV Seams. Click the Unwrap button
and the mesh will be unwrapped again with the same UV shells and no overlap (Figure 9.23).
It is also possible at this phase to place your UVs outside the 0 to 1 texture space. This
will allow you to use polygroups to organize your mesh in ZBrush for easy masking and
hiding as well as enable you to maximize texture space and extract maps for each body part
instead of a single map for the entire model.Figure 9.19 Overlapping UVs
Figure 9.20 New
From UV Check
button