Graphics Programs Reference
In-Depth Information
Click the Color Joints check box to set a different color for each joint in the bind,
which can make for an easier workflow. The Bind Method parameter deals with how the
points in the model are attached. The default, Closest Point, organizes the points into
skin point sets according the joint to which they're closest. They're then assigned to be
influenced by that joint only.
The Partition Set option lets you define your own points before you bind and select
which points are set to which joints. If you define a partition set for each joint you have,
Maya assigns each set to the nearest joint. For example, you can define some points at
the top of the surface to be a part of a set controlled by a joint in the bottom part. Closest
Point is the best option for most work.
Use the defaults, turn on Color Joints, and click the Bind Skin button in the option
box. The root of the skeleton is selected and the cylinder turns magenta, signifying that it
has input connections (such as history).
CREATInG A SMOOTH BInD
A smooth bind allows a joint to influence more than one skin point on the model. This
lets areas of the model farther from the joint bend when that joint rotates. Joints influ-
ence points to varying degrees between 0 and 1 across the surface, decreasing in influence
the farther the point is from the joint. The multiple influences on a point need to add to
1 across all the joints that influence it. Maya automatically generates the proper influence
amounts upon binding, although the animator can change these values later.
To create a smooth bind, select the second skeleton and its cylinder, and choose Skin
Bind Skin Smooth Bind r .
In the option box, you'll find the familiar Bind To parameter. You'll also find, under
the Bind Method drop-down menu, the options Closest in Hierarchy and Closest
Distance. Choosing Closest in Hierarchy assigns the skin points to the nearest joint in
the hierarchy. This option is most commonly used for character work, because it pays
attention to the way the skeleton is laid out. For example, a surface point on the right leg
wouldn't be affected by the thigh joint on the left leg simply because it's near it on the
model. Closest Distance, on the other hand, disregards a joint's position in the hierarchy
of the skeleton and assigns influences according to how far the point is from the joint.
Max Influences sets a limit on how many joints can affect a single point. Dropoff Rate
determines how a joint's influence diminishes on points farther from it. For example,
with Smooth Bind, one shoulder joint can influence, to varying degrees, points stretch-
ing down the arm and into the chest and belly. By limiting these two parameters, you can
control how much of your model is pulled along by a particular joint.
Using all the defaults is typically best. So, click Bind Skin in the option box to smooth-
bind your second cylinder to the bones.
Bend both cylinders to get a feel for how each creases at the bending joints. Figure 9.33
shows the difference.
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