■ Retopology 237Retopology
The ZBrush Topology tools allow you to build new geometry directly on top of an existing
ZTool. You achieve this by making chains of ZSpheres that represent the polygon edges using
the original ZTool as a template or base. Building new geometry in this way makes it possible
to create costume elements that are custom fit to your characters. It is also possible to use the
projection feature to shrink-wrap your new topology to a high-res ZTool, effectively captur-
ing all your sculpted details while completely rebuilding the underlying topology. This is a
huge advantage since it is not possible to change topology in a ZTool without losing all your
sculpting detail. There are two reasons you may want to change the model’s topology: you
want to adjust edge flow to remedy polygon stretching or loss of detail, or you want to create
an animation-ready mesh for use in an external animation and rendering package.
This tool allows you to start a character from just a polygon sphere and carry it all
the way through to polypainting. By using projection in topology, you can project not just
sculpted details but painted color as well. In the following section we’ll rebuild the topology
of the head from Chapter 2, “Sculpting in ZBrush,” into a mesh that can be animated. The
process of rebuilding a model’s geometry is called retopologizing, or sometimes remeshing,
but don’t confuse this with the RemeshAll button under Tool → Subtool. That is a different
process entirely. For a video of this tutorial, please see the accompanying DVD.
Preparing for Retopology
When you’re trying to build an animation-ready mesh on your ZTools, it is often useful to have
the topology planned out ahead of time using the PolyPaint tools. By polypainting the edge
flow on the head first, you can work out topology issues ahead of time. Having the edge flow
drawn on with polypainting allows you to trace the lines when you are using the Topology
tools, which is simpler than trying to plan and execute a retopology on the fly.
- With the head sculpt in Edit mode, turn on Colorize under the main
To ol → Texture menu. Select the Standard brush and make sure only
RGB is on. Have a material selected that will make it easy to see the
lines as you draw; I selected the Fast Shader. - Select white in the active color palette. Choose the main Color
menu, and click the Fill Object button. This will fill the colorized
head with white so you can draw the edge flow plan over it in black. - Switch the active color to black and turn on X Symmetry by press-
ing the X key. Begin by drawing on the eye and mouth loops, as
Figure 7.22 shows. - Establish the main loops you want in the topology
around the eyes, mouth, and overall face. Edge
loops assist in animation, ensuring the mesh can
be deformed naturally with minimal stretching.
Usually you want major forms to be contained
with edge loops (Figure 7.23). - Continuing with the Standard brush, sketch
in the remainder of the topology (Figure 7.24).
When you are done, save the ZTool. The poly-
paint color will save with the file here.
Figure 7.22 Starting loopsFigure 7.23 Topology sketch continues, taking care to
loop the major forms and keep everything a quad