Graphics Reference
In-Depth Information
Rotation.
Normal
is selected for the alternate transformation space. When dealing with bones, using
Normal space always aligns with the current pose of the bone, meaning that the rotation manipulator
provides a convenient interface for rotating bones during animation. Note that the colors of the Rotation
widget match the ones on the miniature 3D axis in the lower left corner of the 3D view. The mini-axis
is labeled: red for
x
, green for
y
, and blue for
z
(RGB =
xyz
).
So, to determine which rotation axes to disable in the Inverse Kinematics panel, enable the Rotation widget
and set it to Normal. You can see in
Figure 9.17
that the red orbit on the widget aligns with the type of
rotation we want to allow for the knee, and red =
x
. We want to allow rotation around the
x
axis, but
not the others. Disable
y
and
z
in the panel and try moving the heel bone. This time, the motion of the
leg bones is closer to real life, with the knee only capable of bending along a single axis.
In addition to being able to toggle Rotation on and off completely, you can also restrict it within a certain
range.
Figure 9.18
shows the collarbone, with restrictions set on both its
x
and
z
axes. The
y
axis has been
completely disabled. Notice the restriction values in the Inverse Kinematics panel, and the corresponding
image in the 3D view. Restrictions are visualized on selected bones by showing the range around which
the bone can rotate. With the collarbone set in this way, it will not move outside of this area when driven
by Inverse Kinematics. Of course, if the collarbone isn't part of an IK chain, these restrictions mean
Figure 9.18
The collarbone with IK rotation restrictions.
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