8

782 Chapter 8: Modifiers
By default, each vertex that’s affected by a single
bone is given a
weight value of 1.0, w hich means
it’s affected by that bone only. Vertices within
the intersection of two bones’ envelopes have two
weight values: one for each bone. And you can
use Skin modifier toolsets such as the
Wei g ht To ol
dialog (p age 1–796)
to arbitrarily assign vertices
toanynumberofbones.Theratioofavertex’s
weightvalues,whichalwaystotal1.0,determine
therelativeextenttowhicheachbone’smotion
affects the vertex. For example, if a vertex’s weight
with respect to
bone 1 is 0.8 and its weight with
respect to
bone 2 is 0.2, then the mot ion of bone 1
will have four times greater influence on the vertex
than will the motion of
bone 2 .
The initial envelope shape and position depends
onthetypeofboneobject.Bonescreatealinear
envelope that extends along the longest axis of the
bone geometr y. Spline objects create envelopes
that follow the c urve of the spline. Primitive
objectscreateanenvelopethatfollowsthelongest
axis of the object.
You can a lso deform the mesh based on the ang le
of the bones. T hree deformers let you shape the
mesh based on bone angles:
• The Joint and Bulge Angle deformers use a
lattice similar to an
FFD lattice (page 1–674) to
shape the mesh at a specific angle.
• The Morph Angle Deformer morphs the mesh
at specified angles. Morph targets are created
by using modifiers above the Skin modifier
in the stack, or by using the
Snapshot tool
(page 1–438)
to create a copy of the mesh and
deforming the mesh using standard tools.
Yo u c a n a p p l y t h e S k i n m o d i f i e r t o s e v e r a l o b j e c t s
at the same time.
Jacket object deformed using the Sk in modifier
In 3ds Max you can mirror envelope and vertex
assig n ments f rom one side of the mesh to the other
with commands on the Mirror Parameters rollout.
Procedures
To use the Skin modifier:
1.
Prepare the skin (mesh or patch object) and
skeleton (bones or other objects). Carefully
place the skeleton inside t he m esh or p atch
objectsothatitselementsareabletoinfluence
polygons or patches in the ir immediate vicinity.
2. Select the mesh or patch object and apply the
Skin modifier.
3. In the Parameters rollout, click Add and choose
the skeleton objects.
4. Click Edit Envelo pes and select an envelope
tomodifythevolumeinwhicheachbonecan
influence the surrounding geometry.
To weight ver tices manually:
1.
On the Parameters rollout, turn on Vertices.
2. Onthemesh,selecttheverticesyouwouldlike
to weight manually.
Each selected vertex is surrounded by a sma ll
white rectangle.
3. highlight the name of the bone for which you
want to change the vertex weights.