Active rendering is a style of programming that allows Java code to handle all of the rendering in a simple while loop. This approach resembles traditional game programming, allowing more time to be spent developing a game and less time spent worrying about which paint method to override.

What is Active Rendering?

There are two different kinds of rendering: active and passive. Anyone who has ever written a swing application has experienced passive rendering. The drawing code is placed in a paint method and the code is called in response to repaint requests. These can come from the code itself, but may also come from the operating system in response to events such as resizing a window or clicking on a component.

Figure 1 shows an example of Passive rendering. There is nothing wrong with letting java handle painting for you, but it is not the only way to develop an application.

Figure 1 - Passive Rendering

Active rendering (Figure 2) is just the opposite. Instead of letting someone else decide when to paint, the program constantly repaints the screen in a very tight while loop. While this sort of behavior is not recommended for regular applications, it is exactly the kind of control needed to make computer games.

Figure 2 - Active Rendering

Why use Active Rendering?

public class Game {

    public static void main(String [] args) {
        setup();
        while( isRunning() ) {
            gameLoop();
        }
        shutDown();
        System.exit(0);
    }
}

Active Rendering in a Window