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482 Chapter 20: Managing Scenes and Projects
retarget references between the incoming nodes
in regards to their scale dependency. Retargeting
means to scale the animation so it matches the
objects onto which you are mapping the motion.
You need to retarget only when the size or
proportions of the incoming model differ from the
size or proportions of the current model.
Retargeting applies to any kind of animation, from
matching fight choreog raphies, to changing a
weatherballoon’sfly-throughtrajectoryoverhills
and val leys. The down side of this is that essentially
youhavetosetupthescalingrelationshipsby
hand; the good news is th at the steps are fairly
straightforward, and that once you have retargeted,
the settings are reusable for all animation mapped
between the same two sets of objects.
While retargeting is a general-purpose feature, it is
especially useful for transferring animat ion from
one character to another, when the characters
are of d ifferent sizes, and possibly of different
proportions (for example, a human model to
a gorilla, or vice versa). You c an transfer IK
animation onto an FK rig, or vice versa. There are
some rules of thumb when you work with mapping
character animation:
• In a walk cycle, the root of a character moves,
and all other movement is typically rotation.
Because of this, usually you want to map t he
root motion and the rotation tracks, and lea ve
the others alone.
The exception to this is when arms or other
parts (tentacles?) are animated by IK. When IK
is present, you need to take the additional step
of mapping and retargeting the IK goals.
• The legs need to reach the “g round,” and feet
should not slide.
Because of this, use t he legs as the basis of
recalculatingthescaleforthetargetcharacter.
• Characters are usually sy m metrical.
Because of this, usually retargeting one limb
does the trick for both.
If a character’s limbs are not symmetrical,
retarget each of them individually. If the current
model uses forward kinematics, then use the
FKRetargetingExtentcontrolsaswell.
Procedure
To retarget one character onto another:
This procedure is not a detailed procedure, but
an overall workflow. It assumes you have already
saved the incoming character’s animation, then
loaded it onto the c urrent character, as described
in To use the Save Animation and Load Animation
comm ands (page 3–472).
Note: If the animation you are saving is unkeyed
world-space animation (as opposed to IK or FK),
turn off Animated Tracks when you save.
1. On the Map Track To Track rollout (page
3–481), map the motion tracks of the incoming
character’s root to the current character’s root.
For example, if you are retargeting a Biped
(page 2–843) onto another, you would map the
incoming Biped object’s position and rotation
tracks onto the current Biped.
2. Map the rotation tracks of the incoming
character’s l imbs onto the current character’s
limbs.
There is one exception here: if a hand (for
example) is going to use IK in the current
scene, either don’t map it at all, so you can
animate it later, or if you are mapping from an
FK model to an IK model, map the Exposed
World Transform to transfer the incoming FK
trajectories to current IK controls.
3. Go to the Retargeting rollout.
4. In the Scale Origin group, choose both the
Incoming and Current root objects.