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792 Chapter 8: Modifiers
By default, ea ch vertex that’s affected by a single
bone is given a weight value of 1.0, which 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 m odifier toolsets such as the We ight Tool
dialog (page 1–807) to arbitrari ly assig n 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 motion 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 geometry. Spline objects create envelopes
that follow the curve of the spline. Primitive
objectscreateanenvelopethatfollowsthelongest
axis of the object.
You can also deform the mesh based on the angle
of the bones. Three deformers let you shape the
mesh based on b one angles:
• The Joint and Bulge Angle deformers use a
lattice similar to an FFD lattice (page 1–683) to
shape the mesh at a specific angle.
• The Morph Angle Deformer morphs the mesh
at specified angles. Morph t argets are created
by using modifiers above the Skin modifier
in the stack, or by using the Snapshot tool
(page 1–453) 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 Skin modifier
In 3ds Max you can mirror envelope and vertex
assig n ments from one side of the mesh to the other
with commands on the Mirror Parameters rollout.
Procedures
To use the Sk in modifier:
1.
Prepare the skin (mesh or patch object) and
skeleton (bones or other objects). Carefully
place the skeleton inside the mesh or patch
objectsothatitselementsareabletoinfluence
polygons or patches in their 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 Envelopes 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 small
white rectangle.
3. highlight the name of the bone for which you
want to change the vertex weights.