Killer Game Programming in Java

Chapter 2. An Animation Framework

A core technology for a good game is an animation algorithm that produces reliably fast game play across various operating systems (e.g., flavors of Windows, Linux, and Macintosh), and in different kinds of Java programs (e.g., applets, windowed, and full-screen applications).

Tip

I distinguish between windowed and full-screen applications because J2SE 1.4 introduced full-screen exclusive mode(FSEM). It suspends the normal windowing environment and allows an application to access the underlying graphics hardware more directly. FSEM permits techniques such as page flipping and provides control over the screen's resolution and image depth. The principal aim of FSEM is to accelerate graphics-intensive applications, such as games.

The common ground between windowed and full-screen application is the game's animation algorithm, which is the subject of this chapter.

The algorithm is embedded in a JPanel subclass (called GamePanel), which acts as a canvas for drawing 2D graphics (e.g., lines, circles, text, images). The animation is managed by a thread, which ensures that it progresses at a consistent rate, as independent of the vagaries of the hardware and OS as possible. The rate is measured in terms of frames per second (FPS), where a frame corresponds to a single rendering of the application to the canvas.

GamePanel is gradually refined and expanded through the chapter, introducing the following notions:

• The {update, render, sleep} animation loop

• Starting ...