Killer Game Programming in Java

Defining a Sprite

A general-purpose Sprite class is hard to design since many of its features depend on the application and the gaming context.

For example, a sprite's on-screen movement greatly depends on the type of game. In Tetris, Breakout, and Space Invaders (and many more), the sprite moves within the gaming area while the background scenery remains stationary. In some of these games, the sprite may be unable to move beyond the edges of the panel, while in others it can wrap around to the opposite edge. In side-scrolling games, such as Super Mario, the sprite hardly moves (perhaps only up and down); instead the background shifts behind it.

A sprite must monitor the game environment, for example, reacting to collisions with different sprites or stopping when it encounters an obstacle. Collision processing can be split into two basic categories: collision detection and collision response, with the range of responses being application specific. Many varieties of collision detection exist: a sprite may be represented by a single bounding box, a reduced size bounding box, or several bounding areas. Examples of each are shown in Figure 11-3 where the bounding regions are the dashed boxes around the pigeon and donkey.

Figure 11-3. Three types of collision detection

A single bounding box is simple to manipulate but prone to inaccuracy. The reduced bounding box is better, but choosing a ...