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698 Chapter 14: Character Studio
nearby vertices. Envelopes typically overlap
at the parent and child ends of links. Vertices
w ithin overlapping envelopes are blended to
create smooth skin deformation over joints as
the charac ter moves.
Adjus t Ski n B ehav ior
Adjust Physique parameters and introduce
skin behavior effects to achieve the desired
characterization.
• Change default envelope shapes by adding cross
sections and control points to isolate a more
specific volume of vertices for each bone. Use
exclusion lists or per-vertex weighting to apply
fine-tuning control over individual vertices.
• Introduce bulge angles to change muscle shape
based on the ang le of a particular joint. Create
tendons to simulate the motion of tendons
under t he skin, based on link movements.
• Adjust l ink parameters to change skin twisting,
sliding, and creasing as t he biped moves.
Sliding allows the skin to compress at the biceps
and forearm as the elbow is bent. Tw isting
controlstheamountofskintwistingacrossa
joint intersection.
• Create extra links using 3ds Max bones and
dummy objects for added control. Links can
be added to the abdominal area to control
compression, for example, or to create a link
to animate the chest rising and falling as the
character breathes. If a character has extra
appendages, 3ds Max bones can b e added to
animatethem.Onecommonusageistoadda
bone to animate the jaw.
For further detail, see
Working with Physique
(page 2–927)
.
Animate the Biped Sk eleton
OncetheskinisattachedtoaBipedstructure,you
can freely animate the Biped character and see
then skin behavior update automatically, based on
the current pose.
Tip: SincePhysiqueskindeformationcanslow
visual playback of your Biped animation, you
can temporari ly hide the skin object or reduce
itsresolutioninthemodifierstacktoimprove
performance.
You can a lso choose to develop Biped animations
in a separate scene entirely, and apply them to your
final skinned character when you are satisfied with
your final motion.
A
biped (page 2–701) character is essentially an
integrated hierarchy of bones that you can position
freely using keyf rames, IK goals, and footsteps.
You can position a biped character using a l l
the rotation and transformation tools found in
3ds Max.
Manyofthe3dsMaxcoordinatesystemscanbe
used to position the biped. Local coordinates are
useful to move a limb along its axis (the local X
axis is always the axis along the biped limb); world
coordinates are handy when there is any confusion
regarding which way is up. You can use world
coordinatesasahomebase.In3dsMax,theworld
Zaxisisalwaysup.
Note: Rotationsalwaysoccuraboutthelocalaxis.
Use Freefor m Techniq ues
Biped provides a variety of methods for creating
character motion easi ly. You can use a purely
traditional approach by manually creating
keyframes in freeform mode for different poses,
letting the computer interpolate between joint
positions and IK goals.
Use a Footstep-Dr iven Technique
You can also choose a par tially assisted approach
by using footsteps and Biped dynamics to help
you create a default walk, run, or jump cycle, and