9

Deformable Envelope 927
Deformable Envelope
In Physique (page 2–1076), envelopes (page
3–934) follow the Physique deformation spline
(page 3–927) that runs through the joints in the
skeleton’s hierarchy. A deformable (as opposed to
rigid) envelope is one that moves the mesh vertices
it encloses as the skeleton moves.
Alinkcanhavebothadeformableandarigid
envelope. When it has both, the effect of the two is
averaged, creating a less flexible skin.
In character animation, yo u typically use
deformable envelopes; however, some portions of
the body, such as the head, mig ht lo ok best if they
are rigid.
Note: Because of game-engine restrictions, if you
are developing for certain engines, you might want
to use rigid en velopes exclusively.
Tip: If your model consists of articulated rigid
segments, such as a marionette, you might not
need to u se Physique at all. Simply link each part
to the corresponding biped object.
Defor ma tion
The effect caused by Physique (page 2–1076) on
a mesh. Envelopes, bulges, link parameters, and
tendons all affec t how a mesh deforms.
Defor ma tion Spline
The deformation spline is created when you
initialize Physique (page 2–1076).Itisacontinuous
curve through several points. The deformation
spline is a smooth curve that runs from joint to
joint.
The deformation spline displays as a yellow curve that runs
through the mesh.
The Bend, Bias, and Tension spinners can change
the shape of the deformation spline.
The deformation spline also takes into
consideration twisting and scaling of the skeleton’s
links. At the Link sub-object level (page 2–1135),
you take con trol of the behavior of the deformation
spline, and subsequently gain full control of the
skin’s behavior relative to the skeleton’s movement.
Degree
Thedegreeofacurveisthehighestexponentin
the equation used to represent it. A linear equation
is degree 1, a quadratic equation degree 2. NURBS