9

Freeform Animation 887
addafootstepanimationtoanexistingfreeform,
you can use the motion flow editor to create a script
that sequences the footstep with the freeform.
Inverse K inematics
Footstep a nd freeform animations use the same
inverse kinematics (page 3–958) 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
star t and end of a sequence of IK constraints in
WorldSpacewithanIKBlendvaluegreaterthan0.
Deleting and inserting keys or changing IK space
or IK blending alters footstep duration.
Incasesinvolvingeditsthatalterthelengthof
ballistic intervals (w hen a biped is airborne),
the software ensures that there is a ver tical key
occurring at the lift-off and touchdown frames.
This calculate s the correct ballistic motion, so
vertical keys are automatically inserted if not
present.
There are three types of IK keys you can create:
planted, sliding and free keys.
• Planted keys have an IK Blend of 1. They are
joined to the Previous IK Key and are in Object
space, rather than Body space. Planted keys
lockthefootorhandtotheground,ortoany
object.
• Slid in g keys have moving IK constraints.
Sliding footsteps are created if there is a moved
IK constraint occurring in the footstep interval.
In a footstep animation this means that the foot
can be placed anywhere, even though there is
a footstep icon. Footstep icons can be thought
of as gizmos r ather than the absolute location
of a foot. Sliding keys have a n I K blend of 1,
and are in object space, but are not joined to the
previous IK key.
• Free keys have an IK blend of 0, and are in body
space. They are not joined to the previous IK
key. Free keys have no IK constraint.
IK constraints are implemented with a pivot-based
system. This allows you to pivot a hand or foot
around a selected pivot. For example, in a walking
motion you can select a pivot on the heel of a foot
and rotate the foot around it,. You can then shift
the pivot to the b all of the foot.
Procedures
To create a purel y f reef orm a nima tion:
1.
Create a biped.
2. Movethetimeslidertoanygivenframethendo
one of the following:
• Turn on Auto Key, then mov e or
rotate any biped component. This sets a key
for that component.
•
Pose any p art of the biped, then in the
Key Info rollout, click Set Key .
•
Pose the hands and feet and then in the
Key Info rollout click Set Plante d Key . This
will create keys that cause the hands or feet
to stick in space.
For more information on setting keys, see
Setting Keys for Feet and Hands (page 2–904).
Note: character studio doesn’t behave the
same as 3ds Max w hen creating keys. It doesn’t
automatically create keys at frame 0 when you
create your first set of keys at a later frame. For
this reason, it’s often usefu l to select all the
parts of the biped at frame 0, then click S et Key
to creating holding keys for al l.
To create a f r eefr om a nimat ion fr om a footstep
animation:
1.
Selectthebipedwhosefootstepanimationyou
want to convert to freeform.
2. On the Motion panel Biped rollout, click
Convert.