Shapes and Morphing - Blender Foundations: The Essential Guide to Learning Blender 2.6 - page 284

expression. One way to work is to create,
for example, an entire smile that encom-
passes all areas of the face. However, you
could just as well create a smile for the
mouth only, which when combined
with separate shape keys for bunched
cheeks, squinting eyes, and a drawn chin,
would produce a full face smile. While
obviously more labor intensive, this
approach is more flexible, allowing you
to create subtle expressions by reducing
or increasing the Value sliders of different
sections of the face.

Shape Keys can also be applied over a
greater range of values than just 0-1.0.
The allowable range is controlled by the
Min and Max range sliders. Setting these
to −1.0 and 2.0 for the smile shape
shown in Figure 10.2 lets you push the
shapes past how you modeled them, in
both directions. Figure 10.4 shows the
smile pushed to 200% (2.0), which is clearly a bit maniacal,
and pulled down to −1.0. It's not exactly a frown, but you
can see that the Shape Keys system is capable of usefully
going beyond the bounds of your original work.

Figure 10.2, cont'd

The Blend field allows you to specify a masking vertex
group. The smile used in the example has more going for
it than just a rotation at the corners of the mouth. The
entire geometry of the face has been adjusted: checks, chin,
eye shape, and brows. We'll get into that in the next
section, but for now let's say that you liked your smile
shape, but wanted to create an additional shape key for a
“dead” smile—one that worked for the mouth only but left
the eyes alone.

Figure 10.3 The Shape Keys panel, ready to work.

First, you would create a vertex group for the area around and including the mouth. The easiest way to
do this is to click the + button on the Vertex Groups panel, name the new group “mouth,” then drop
in to Weight Paint mode with Ctrl-Tab. Paint the area around the mouth, then return to Object mode.
Down in the Blend field for the smile shape key, select the new “mouth” vertex group. The shape key
is displayed only for the areas that fall within the vertex group. To make a new key using only this masked