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744 Chapter 14: Character Studio
While character studio calculates vertical
dynamics and gravit y based on its footstep-driven
technology, you don’t always want your character
str ic tly under these controls. You might want
the character to fly, sw im, or to do something
improbable in a physical world. For these
situations, Biped supports a comprehensive set of
freeform animation controls that allow you to take
total creative control over your character’s pose,
movement, and timi ng.
character studio gives you the option to animate
characters using freeform mode exclusively, or
to create freeform periods during a footstep
animation. In freeform mode (without footsteps),
you can pose every joint of your character exactly
as you like using traditional keyframe methods.
Handsandfeetcanbelockeddowninspaceby
setting planted keys. You can also animate the
pivot points for hands and feet to simulate rolling
motion. You can blend dynamically between
forward kinematics and inverse kinematics to
introduce hig her-level control.
To use freeform animation in Footstep mode,
you create freeform periods between footsteps
using Track View – D ope Sheet. You can convert
an existing footstep animation into a freeform
animat ion and back again. This lets you mix the
use of footstep and freeform methods.
Wa rn in g : You can’t add a freeform period at the
beginning or end o f a footstep animation.
Tip: If you want to do this, stretch out the timing for the
first or last set of footsteps, then convert the footstep
animation to freeform.
Fr e eform Meth o d
A freeform animation con tains no footsteps;
instead it relies on the transforms of the biped
body objects and center of mass. Use Freeform for
motions like swimming or falling where footsteps
are not necessary. If you are a familiar with
creat ing a ll of your keyfr ames manually to animate
a character , y ou may want to use the freeform
method exclusively.
To start a f reeform animation, turn on Auto Key
and start positioning the biped. You can also leave
Auto Key off and use the red set key buttons on t he
Key Info rollout (p age 2–809) to create keyframes.
You can also create freeform animation by
importing motion capture data and choosing
freeform rather than footstep.
Tip: Take advantage of both methods by combining
footsteps and freeform animation. You can create
a freeform period for any airborne period between
footsteps. A freeform period replaces the ballistic
motion calculated using the GravAccel value with
auserdefinedsplinemotion.
If you are using footstep extraction with motion
capture data, you often need a freeform interva l to
accommodate falling or tumbling motion in the
data.TheFittoExistingoptionontheMotion
Capture Conversion Parameters dialog allows
for a combination of both methods. Extracting
footsteps from motion capture files eliminates
sliding feet, a common problem with motion
capture data.
Notethatwhileyoucanaddafreeformperiodto
a footstep animation, you
cannot add a footstep
period into a freeform animation. If you want to
add a footstep animation to an existing freeform,
you can use the motion flow editor to create a script
that sequences the footstep with the freeform.
Inverse K inematics
Footstep and freeform animations use the same
inverse kinematics (page 3–1052) constraints
and extensions. This means that in a footstep
animation, you can now edit keys to change
footstep duration. By definition, a footstep is the
start and end of a sequence of IK constraints in
Wor l d Space w ith an I K B l e nd v a lue g reat er t h a n 0 .