Datasheet

Unpacking Our Toolkit ■ 15
The heart of Samples is Sample Radius (see Figure 1.16). This is the shock absorber
of the entire system. In simple terms, Sample Radius determines whether your brush’s
response to the road is light and snappy to the road or whether it bulldozes through any
surface variation.
In more specific terms, Sample Radius determines how much of the area within your
brush’s sphere of influence will be used to calculate the orientation of your brush. By
default, Sample Radius should be set to provide a quick but not hypersensitive response
to your surface. Think Porsche. For most brushes this is .75, but this does vary.
As you decrease this number, ZBrush considers a smaller and smaller percentage of
the surface area. This makes it much more responsive to changes in the surface direction
and makes for a very bumpy ride.
Another way to think about this is with a boat analogy. A smaller boat has a smaller
area of the water’s surface to sample from, so it is more sensitive to waves and swells. A
cruise ship, on the other hand, has a vastly larger area of the water’s surface to sample
from and is therefore much more stable. However, a cruise ship can’t be turned on a dime
as a smaller boat can. The trade-off is the same in ZBrush: stability for maneuverability.
The other features that influence the brush’s stability and maneuvering are as follows:
Stabilize Orientation•
Stabilize Direction•
Constant Sample•
OnSurface•
Preserve Edge•
Buildup•
All these features work together to give you the ride you need for the form you are try-
ing to create. When adjusting them, it is useful to keep in mind that Sample Radius is the
main influence. Everything else works to help Sample Radius do its job.
Trim Adaptive
Trim Adaptive is built to give us a more controlled experience. If used freehand style,
it can get a little too aggressive. If used in a controlled manner, though, it creates clean
planes that would be very hard to create any other way. At the core of its control is a fea-
ture in ZBrush that hasn’t received a lot of attention: orientation.