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812 Chapter 8: Modifiers
Sk in Morph Modifier
The Skin Morph modifier lets you use a bone ’s
rotation to drive a morph; that is, a deformation
of the object mesh. Skin Morph is intended for
use with a Skin or comparable modifier (e.g.,
Physique); add the Skin Morph modifier after
the skin-type modifier. You create the morph at
the frame in which the effect should be greatest,
andthenSkinMorphautomaticallyanimatesthe
affected vertices into and out of the morph, based
on the rotation of the bone that drives the morph.
This lets you fine-tune mesh deformation at any
frame, using a bone to dr ive the m orph that is
fixing a problem area. Typically, when animating a
character with bones, an ar t ist has to create extra
bones to handle problem areas such as armpits and
groinareas.WithSkinMorph,insteadofusing
extra bones, you can simply create a morph, and
then transform vertices into the exact shape you
want. Skin Morph lets you easily create muscle
bulges and many other effects.
Note: When working with Skin Morph, it’s
important to be familiar with the concept of
delta.Theframeatwhichyouapplythemodifier
determines the base position for each vertex that’s
used in a morphing animation controlled by Skin
Morph.Afterapplyingthemodifier,gotoaframe
at which the bone driving the morph is rotated an
amount that will cause the greatest deformation,
and then tr ansform vertices to produce the morph.
Theamountbywhichyoutransformthevertices
is called the delta: the difference between the base
pose and t he morphed p osition.
Procedure
To use Ski n M orph (basic usa ge):
1.
Create an animated character with bones and
askinnedbodymesh,usingamodifiersuchas
Skin (page 1–791) or Physique (page 2 –834).
2. Go to the “pose frame” and apply the Skin
Morph modifier.
Theposeframecontainstheinitialpose;
typically a standing character with arms
outstretched and legs apart. This is often
frame0,butitcanbeanyframe,evena
negative-numbered one. This is the frame from
which t he modifier measures delta: the change
in the vertex position between this pose and
the morph.
3. Determine which bones are driv ing
deformations that you want to modify with
Skin Morph.
For example, bending an arm might cause the
inside of the elbow to indent too far, or you
mightwanttoaddabulgingbicep.Inthiscase,
the forearm bone is driving the deformation.
4. UseAddtobindthedeformation-drivingbones
to the modifier.
The mo difier overlays an orange line along the
length of each bone you add.
5. Go to the frame where you wish to create the
morph. Using the arm-bending example, this
might be the frame where the forearm is at a
90-degree angle to the upper arm.
6. In the list bo x, click one of the bones.
Intheviewport,theorangelinerepresenting
the bone becomes a thicker yellow line to
indicate that this bone w ill drive the morph.
7. On the Lo cal Properties rollout, click Create
Morph.
The modifier adds a morph to the highlighted
bone and sets the morph to 100% at this f r ame,
as reflected by the number next to the m or ph’s
name in the list.
8. On the L ocal Propert ies rollout, click E dit.
This temporarily f reezes the skin deformation
at the current frame.