9

Using th e Motion Mixer 605
The Motion Mixer is comparable to an audio
mixer. Mot ion clips can be cross-faded, stretched,
layered, and final ly, mixed down to a single clip.
The Motion Mixer works by placing motion files
on tracks (page 3–1023).WiththeMotionMixer,
you can:
•Transitionorfadebetweenmotions.
•Movemotionsintime.
• Trim a motion so only part of it is used.
• Vary the speed of a motion over t ime.
• Use animation from selected biped or
non-biped body parts within a motion clip.
• Keep planted feet from sliding during
foot-based transitions.
ToseeabipedmotionintheMixerapplied
to the biped in the scene, you must turn on Mixer
Mode from the Biped rollout (page 2–936).
In the Motion Mixer, motions are imported and
mixedforanyobjectsinthescene.Oncemotions
aremixed,youcanpassthemixontootherbiped
(if it contains B IP fi les) and non-biped objects (if it
contains XAF files), or save the mix to a MIX file.
B lending M otions in the Mi xer
The Motion Mixer provides these t ypes of motion
blending.
• You can blend motion from one clip to another
with a transition (page 3–1027). Transitions in
the Mixer are similar to those used in the motion
flow system (page 2–1026). The optimization
feature c an automatically find the best t iming
for a t ransition b e tween two clips. When you
make a transition b etween foot-based clips
(clips where IK constraints keep the feet planted
at certain times), you can cause the transition
to focus on one foot or the other . See Working
with Transitions (page 2–616).
• In biped animation, if a transition between
foot-basedclipscausesthefoottoslideor
pop slig htly during the transition, you can fix
this problem with a mixdown (page 3–973)
(flattening a ll tracks into one track). See
Exporting Animation to the Biped (page 2–624).
• You can change the weight (page 2–619) of clips
or tracks so they affect the a nimation more at
some t imes than others. See Adjusting Track
Weight (page 2–619).
• You can use only the part of a clip’s motion that
affects specified bo dy parts. See Filtering Mixer
Tracks (page 2–612).
• When motions applied to a biped’s upper
body vary greatly from motions on its lower
body, the Mixer automatically compensates for
discrepancies in balance. See Adjusting Biped
Balance in the Mixer (page 2–622).
Note: Balance parameters are available only
when mixing biped objects.
Transitions B etween Foot-B ased Clips
The Motion Mixer excels in its ability to maintain
smoothness of motion over transitions between
foot-based clips. Foot-based clips use IK
constraints to keep one or b oth feet locked down
over the course of the motion.
For bipeds, the Mixer provides tools for
maintainin g foot positions during transitions:
• Computing the influence of balance from the
uppertothelowerbody.Withoutthis,layered
motion t racks will appear to be artificially
combined since out since the resulting motion
will be plagued by the isolation of dynamics
and improper b a lance.
• Mixdowns allow for precise elimination of
the foot sliding with the aid of knee limit
filtering to u nnatural knee poppimg artifacts.
In short, the goa l of the mixer is to assemble
seamless, coherent character motion us ing