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942 Chapter 14: Character Studio
Choose Initial Skeletal Pose (page 2–950) if you
want to work in the position of the mesh and
itsskeletonatthetimePhysiquewasapplied.
Returning to this p ose can be usef ul if the display
becomes confused with the effects of unassigned
vertices when the character moves through an
animation.
See also
Fine-Tuning Envelopes (page 2–940)
Working with Defor mable
Envelopes
Once you’ve got the deformable envelopes
working the way you want to cont rol overall sk in
deformation, you may want to adjust the finer
aspects of skin control:
• Skin bending, twis ting, sliding, and scaling
about single links are controlled at the Link
sub-object level. See
Adjusting Link Parameters
(page 2–943)
.
• Link sub-object primarily controls the
deformation spline (page 3–1021) .Youuse
Link sub-object options to affect the shape of
the spline and the smoothness of the skin. See
Adjusting Link Parameters (page 2–943) .
• Crease behavior where links meet and bend
is controlled at the L in k sub-object level w ith
Joint Intersec t ion (page 2–991) parameters.
• Musclebulgesasyourcharacter’slimbsmove
through a range of motion are controlled at the
Bulge sub-object level. See
Creating Bulges
(page 2–946)
.
• Skin stretching, generally between
non-contiguous links, is controlled at the
Tendon sub-object level. Tendons provide a
secondary movement (a pulling or stretching)
basedonlinksfartherupordowntheskeleton.
See
Creating Tendons (page 2–948) .
See also
Link Sub-Object (page 2–986)
Bulge Sub-Object (page 2–992)
Tendons Sub-Object (page 2–998)
Working with Rigid Envelopes
Vertice s influenced by a rigid envelope follow the
link itself rather than the deformation spline, like
deformable vertices do. Low vertex-count models
used for games are typically connected to the
skeletons with rigid envelopes to simplify export
to game eng ines. In such a case, each vertex can b e
simply described as assig ned to a specific link. It
canbelocatedbygivingalengthalongthelink,a
distance from the center of the link, and an ang le
around the link. As the link is transformed, all
the vertices assigned to the vertex are uniformly
transformed. This makes it simple for game
engines to move the character’s skin.
Theverticesmoveequallywiththecontrolling
link, so the skin appears rig id. For instance, in the
caseofaflexingarm,theskinbetweenthewrist
and elb ow tightly follows the movement of the
forearm, with no change in the spacing between
vertices. The skin between the elbow and shoulder
tightly follows the upper arm. Vertices around the
elbow influenced by both links, smoothly blend
to an average pos ition between the two changed
links.
Rigid and deformable envelopes can be mixed on
a g iven character. You might, for instance, use
deformable envelopes for most of the character,
but choose rigid for the head and for a suit of
armor around the torso.
Note: InLinksub-object,youcanturnontwisting
for rigid envelopes. As the wrist tw ists the vertices
on the forearm will twist also.