8

944 Chapter 14: Character Studio
than 180 degrees, the skin moves toward the
joint.Ontheinside,thesidewherethejoint
angle is less than 180 degrees, the sk in moves
away from the joint.
The sliding effect tightens the outside to keep
detail at the joint and prevent the facets of the
mesh from moving apart. It relaxes the inside to
prevent the mesh f rom bunching up at the joint.
• Radial Scale parameters affect the influence on
the skin caused by scaling links of the skeleton.
Certain settings, such as Breathe and Stretch,
react to scaling of the skeleton, but only with
standard 3ds Max b ones or a 3ds Max hierarchy.
Note: Bipeds and 3ds Max IK controllers do n’t
support scaling.
LinkScaleprovidesawaytogloballyscale
all the vertices influenced by the link. CS
Amplitude scales the effect of bulge cross
sect ions across the entire link. It can be used
for animated scaling of the bones or for general
mesh adjustments. The i ntent is not to edit the
character itself, but rather the effect the bones
have on it.
You set Link parameters at the sub-object level, in
the
Physique Link Settings rollout (page 2–987) .
Par tial Blending and Weight
Assignments
Most often, you will want to use envelopes to
correct the way skin behaves as the biped moves.
However, you can override envelopes by manually
assigning vertex properties. For example, you can
removetheinfluenceofinappropriatelinksfrom
selected vertices. You can also change the weight
distribution between links for a single vertex by
using type-in weights.
InCaseswhereNoEnvelopesUsePartial
B lendi ng (t he D efa ult)
Ve r t e x v is assigned to links l1, l2, and l3 ,andthe
weights for these links are:
w1 =0.2, w2 =0.3,and
w3 =0.4.
In a non-part ia l blended case, the sum of these
vertex weights is
w1+w2+w3=0.9 (less than
1.0).
With partia l blending off, Physique wi ll normalize
the weights so they sum to 1.0. For example:
w1’ = w1 / w1+w2+w3 = 0.2/0.9 = .2222222...
w2’ = w2 / w1+w2+w3 = 0.3/0.9 = .3333333...
w3’ = w3 / w1+w2+w3 = 0.4/0.9 = .4444444...
so
w1’+w2’+w3’ = 1.0
In Cases where All Envelopes Use Par t ial
Blending
The weight fill-in for vertices with a weight less
than1willalwaysfillwiththeweightoftheroot.
Whenever a vertex is assig ned to a group of
links, all of which are partially blended, then the
remaining weight w i l l be assig ned and blended
w ith the root link.
This works well for a case where you want partial
deformation falling off to no deformation. An
examplewouldbeastatichead,whereyouare
deforming the head for facial expressions, but the
head itself remains in place.
For example: vertex
v is assigned to links l1, l2,
and l3. The weights for these links are: w1 =0.2,
w2 =0.3,and w3 =0.4.
Thesumofthesevertexweightsis
w1 + w2 + w3
=
0.9 (less than 1.0). We need an additional fill-in
weight (
wf ). The fill-in weig ht is determined by
1.0 - (w1+w2+w3) = 0.1, or 10%. Physique fills in
with weight
wf from the root (leaving the vertex
partially undeformed).