COMPUTER-ANIMATION LANGUAGES

COMPUTER-ANIMATION LANGUAGES

Design and control of animation sequences are handled with a set of animation

routines. A general-purpose language, such as C, Lisp, Pascal, or FORTRAN, is

often used to program the animation functions, but several specialized animation

languages have been developed. Animation functions include a graphics editor, a

key-frame generator, an in-between generator, and standard graphics routines.

The graphics editor allows us to design and modify object shapes, using spline

surfaces, constructive solid-geometry methods, or other representation schemes.

A typical task in an animation specilkation is scene description. This includes

the positioning of objects and light sources, defining the photometric parameters

(light-source intensities and surface-illumination properties), and setting the

camera parameters (position, orientation, and lens characteristics). Another standard

function is action specifimtion. This involves the layout of motion paths for

the objects and camera. And we need the usual graphics routines: viewing and

perspective transformations, geometric transformations to generate object movements

as a function of accelerations or kinematic path specif~cations,v isible-surface

identification, and the surface-rendering operations.

Key-frame systems are specialized animation languages designed simply

to generate the in-betweens from the user-specified key frames. Usually, each object

in the scene is defined as a set of rigid bodies connected at the joints and with

a limited number of degrees of freedom. As an example, the single-arr.1 robot in

Fig. 16-4 has six degrees of freedom, which are called arm sweep, shoulder

swivel, elbow extension, pitch, yaw, and roll. We can extend the number of degrees

of freedom for this robot arm to nine by allowing three-dimensional translations

for the base (Fig. 16-51. If we also allow base rotations, the robot arm can

have a total of 12 degrees of freedom. The human body, in comparison, has over

200 degrees of freedom.

Parameterized systems allow object-motion characteristics to be specified

as part of the object definitions. The adjustable parameters control such object

characteristics as degrees of freedom, motion limitations, and allowable shape

changes.

Computer-Anmalion

Scripting systems allow object specifications and aninlation sequences to

be defined with a user-input script. From the script, a library of various objects

and motions can be constructed