8

Retargeting Rollout 487
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 choreographies, to changing a
weatherballoon’sfly-throughtrajectoryoverhills
and valleys. The down side of this is that essentially
youhavetosetupthescalingrelationshipsby
hand; the good news is that 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 animation from
one character to another, when the characters
are of different sizes, and possibly of different
proportions (for example, a human model to
a goril la, or vice versa). You can 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 al l other movement is typically rotat ion.
Because of this, usually you want to map the
root motion and the rotation tracks, and leave
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 retarget ing the IK goals.
• The legs need to reach the “ground,” and feet
should not slide.
Because of this, use the legs as the basis of
recalculatingthescaleforthetargetcharacter.
• Characters are usually symmetrical.
Because of this, usually retargeting one limb
does the trick for both.
If a character’s limbs are
not sy mmetr ical,
retarget each of them individually. If the current
model uses forward ki nematics, then use the
FKRetargetingExtentcontrolsaswell.
Procedure
To retarget one character onto another:
This procedure is not a detailed procedu re, but
an overall workflow. It assumes you have already
saved the incoming character’s animation, then
loaded it onto the current character, as described
in
To use the Save Animation and Load Animation
commands (page 3–478)
.
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
3–486)
, map the motion tracks of the incoming
character’s root to the current charac ter’s root.
For example, if you are retargeting a
Biped
(page 2–701)
onto another, y ou would map the
incoming
Biped object’s position and rotation
tracks onto the current
Biped .
2. Map the rotat ion tracks of the incom ing
character’s limbs 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 al l, so you can
animate it later, or if you are m apping from an
FK model to an IK model, map the
Exposed
World Tr ansform
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.