Graphics Programs Reference
In-Depth Information
15.9 Vertex Groups or Field of Influence
Having described the deformation of a mesh by employing vertex
groups and field of influence, the question arises as to which is be-
ing employed when the armature is located inside the mesh. If we
follow the preceding examples by either selecting vertices or weight painting, we
assign vertices to a vertex group. It is unclear whether the vertex group or the field
of influence is controlling the deformation of the mesh. If the armature is moved
away from the mesh posing, the bone will still cause a deformation; therefore, the
vertex group is in control. But when the armature is inside the mesh, is it the field
of influence or the vertex group?
Follow this example to clarify this dilemma. Create the same scene as in Meth-
ods 1 and 2, select only the vertices at the tip of the finger, and assign them to a
vertex group (Figure 15.34). Make sure you have added an armature modifier to
the finger and have assigned “Armature” in the “Object” panel. Rotate “Bone.001”
in pose mode and the whole top of the finger deforms. Place the armature in
object mode and move it away from the finger. Rotate the bone again and only
the tip of the finger deforms—this only proves that both the vertex group and the
field of influence are active.
Place the armature back inside the finger. Select the finger and take a look
at the armature modifier. Under the heading “Bind To” there are the two boxes
labelled “Vertex Group” and “Bone Envelope.” Untick “Bone Envelope”; rotating
the bone now only deforms the tip of the finger (Figure 15.35). Obviously you
have turned the field of influence of, so herein lies the control for selecting either
the field of influence or the vertex group.
Another way of negating the field of influence is to set the “Distance” and
“Weight” values to 0.000 in the properties window - “Bone” button - “Deform” tab (Fig-
ure 15.36). In the properties window - “Object Data” button - “Skeleton” tab, under
“Deform” there are also boxes ticked and labelled “Vertex Group” and “Bone Envelope.”
Ticking or unticking these seems to have no effect.
Figure 15.34
Select the vertices
at the tip only.
Only the tip moves.
Figure 15.35
