About Blend Shapes

Blend Shapes are deformers that let you blend the shape of one object into another. This feature is particularly useful for facial animation and muscle deformation and to fix badly deformed geometry. For example, if you wanted to make a character smile, you could simply duplicate the head, change the shape of the mouth into a smile, and apply the smiling head as a Blend Shape. The one restriction of Blend Shape is that both objects must have the same topology, or surface construction.

To apply a Blend Shape:

1.	Create a NURBS sphere. You may need to add more spans to the sphere to get more detail. I've used 14 sections and 14 spans.
2.	Change the shape of the sphere by moving CVs so that it looks like it has a mouth (Figure 12.83). Figure 12.83. A NURBS sphere modeled to look like a head with a mouth.
3.	Duplicate the sphere and move it away from the original.
4.	Change the shape of the new sphere by moving the CVs so that it looks like it is smiling (Figure 12.84). Figure 12.84. By moving CVs, change the shape of the mouth to a smile.
5.	Duplicate the original sphere again, move it aside, and change its shape so that it looks like it is frowning (Figure 12.85). Figure 12.85. Create a frown shape for the mouth.
6.	-select, in this order; the smile, the frown, and the original head.
7.	From the Deform menu, select Create Blend Shape (Figure 12.86). Figure 12.86. Create a Blend Shape from the Deform menu. This applies the two new shapes to the original head.
8.	From the Window menu select Animation Editors > Blend Shape (Figure 12.87). Figure 12.87. Open the Blend Shape controls from the Animation Editors menu.
9.	In the Blend Shape window adjust the two sliders to see the effect on the original head.
10.	At frame 1, click the Key All button (Figure 12.88). Figure 12.88. Sliders are used to adjust how much the original shape is deformed.
11.	Go to frame 10 and move the first slider all the way up (Figure 12.89). Figure 12.89. The blend shapes can be keyframed over time to create facial animation.
12.	Click the Key All button.
13.	Go to frame 20 and move the first slider down and the second slider up.
14.	Click the Key All button again. Now when you play back the animation, the original head changes its shape from a neutral look to a smile and then to a frown.