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468 Chapter 12: Animation
Activating R otati onal Joints
1. R otational links
WhenyouturnonActiveforoneoftheX,Y,Z
axes of a rotational joint, the object can rotate
about that axis of its parent’s coordinate system.
Joints that rotate about multiple axe s are very
common. A ball joint, like your shoulder, is a
rotational joint active about all three axes. A pin
joint, like your elbow, is a rotational joint active
onasingleaxis.
Activating S liding Joints
1. Sliding ax is
WhenyouturnonActiveforoneoftheX,Y,Z
axes of a sliding joint the object can move along
that axis of its parent’s coordinate system.
Most sliding joints are active only along a single
axis. A telescope is an example of a sliding joint
active on a single axis. You rarely see a sliding joint
active along all three axes.
If a sliding joint is active along all three axes, it
moves independently from its p arent. It’s almost
as if there is no joint connection a t all.
Tip: Use the HD IK Solver w hen you need to use
sliding joints with IK.
Pat h an d Surf a ce Joi nts
Circular path
WhenyouturnonActiveforPathorSurfacejoints
you are setting whether the object can move along
the assig ned path or surface.
A house key on a ring is an example of an active
path joint.
See
Path Constraint (page 2–380) .
Limiting Joint Action
Most joints are limited in their range of motion
along an active axis. For example: a hinge might
open only to 120 degrees; a piston slides only
w ithin the length of its cylinder. To limit the range
of motion allowed on an active axis, you turn on
Limited and set values for the From and To fields
on the joint rollouts.