PROGRESSIVELY ANIMATED GRAPHICAL OVERLAYS
Original Publication Date: 2000-Mar-01
Included in the Prior Art Database: 2003-Jun-18
It has been a common practice a present small animated images either by themselves or superimposed on other images. Examples include the imbedding of animated images in web pages based on the GIF89a image specification (Compuserve), the creatures overlayed on the scenes in Doom (Id software), and the object movies supported by QuickTimeVR (Apple). Such overlaid images are commonly referred to as sprites when they posses a transparent background and when superimposed on a graphical background. In this disclosure, the term "sprite" will be used to refer to an animated overlay irrespective of whether it has a trans- parent background or whether it is superimposed on a graphical background. A simple sprite consists of a series of images which are to be displayed in sequence at a partic- ular rate or number of images per second. After displaying the last image, the sequence may be repeated. Alternatively, one of the images in the sequence may be selected based on some criterion such as the position of a pointer or cursor in a window on a computer screen. Such a sprite may be defined as a "1-d" sprite because all of the constituent images represent the change in a single variable such as time or horizontal motion of a pointing indicator (e.g., mouse cursor. The concept of a sprite may be generalized to include "2d" sprites. Such a sprite may consist of multiple sequences of images. An individual image within such a such a sprite may be selected based on two criteria. For example, the horizontal position of a pointer could be used to select one of the sequences within the sprite, and the vertical position of the same pointer could be used to select an image within the selected sequence. This technique is commonly used to present "object movies" using QuickTimeVR (Apple). The concept of a sprite may be further generalized to include "3d sprites" in which each image in a "2d sprite" is replaced by an "inner sequence" of images. In this case, an image within "inner sequence" may be selected, for example, based on time, with successive images being presented at a specified rate and repeating at the start of a selected "inner sequence" after presenting the last image in each "inner sequence". Each "inner sequence" is a member of a "middle sequence" which may be selected, for example, based on the horizontal position of a pointing indicator. The complete 3d sprite is itself composed of a sequence of middle sequences, and a particular middle sequence may be selected based on, for example, the ver- tical position of a pointing indicator. The QuickTimeVR product from Apple also provides support for such 3d sprites.