Facial Animation - Computer Animation: Algorithms and Techniques - page 322

FIGURE 10.7
Facial design by pushing and pulling surface of high-resolution sphere-like shape [ 17 ] .
FIGURE 10.8
Facial design by initially defining the eyes and mouth regions [ 29 ] .
Besides the interactive design approach, there are two main methods for creating facial models:
digitization using some physical reference and modification of an existing model. The former is useful
when the model of a particular person is desired; the latter is useful when animation control is already
built into a generic model.
As with any model, a physical sculpture of the desired object can be generated with clay, wood, or
plaster and then digitized, most often using a mechanical or magnetic digitizing device. A two-
dimensional, surface-based coordinate grid can be drawn on the physical model, and the polygons
can be digitized on a polygon-by-polygon basis. Post-processing can identify unique vertices, and a
polygonal mesh can be easily generated. The digitization process can be fairly labor intensive when
large numbers of polygons are involved, which makes using an actual person's face a bit problematic.
If a model is used, this approach still requires some artistic talent to generate the physical model, but it
is easy to implement at a relatively low cost if small mechanical digitizers are used.
Laser scanners use a laser to calculate distance to a model surface and can create very accurate
models. They have the advantage of being able to directly digitize a person's face. The scanners sample
the surface at regular intervals to create an unorganized set of surface points. The facial model can be
constructed in a variety of ways. Polygonal models are most commonly generated. Scanners have the