Karen Anders's List: Digital Animation

To create the illusion of movement, an image is displayed on the computer screen then quickly  replaced by a new image that is similar to the previous image, but shifted  slightly. This technique is identical to how the illusion of movement is  achieved with television and motion pictures.

Tweening, short for in-betweening, is the process of generating  intermediate frames between two images to give the appearance that the first  image evolves smoothly into the second image. Inbetweens are the drawings  between the keyframes which help to  create the illusion of motion. Tweening is a key process in all types of animation, including computer  animation. Sophisticated animation software enables one to identify specific objects in  an image and define how they should move and change during the tweening process.  Software may be used to manually render or adjust transitional  frames by hand or use to automatically render transitional frames using interpolation of graphic  parameters.

In engineering and science one often has a number of data  points, as obtained by sampling or experiment, and tries to construct a function which  closely fits those data points. This is called curve fitting or regression analysis. Interpolation is a  specific case of curve fitting, in which the function must go exactly through  the data points.

A different problem which is closely related to interpolation is the  approximation of a complicated function by a simple function. Suppose we know  the function but it is too complex to evaluate efficiently. Then we could pick a  few known data points from the complicated function, creating a lookup table, and try to  interpolate those data points to construct a simpler function. Of course, when  using the simple function to calculate new data points we usually do not receive  the same result as when using the original function, but depending on the  problem domain and the interpolation method used the gain in simplicity might  offset the error.