Chapter 31.   A Networked Two-Person Game

This chapter describes a networked two-person 3D game. The initial implementation lacks networking components, so we can concentrate on issues such as game logic, 3D modeling, and user interface design. In the second stage, networking elements are added, with fairly minimal changes to the basic game.

FourByFour is a 3D version of tic-tac-toe, as shown in image above. Player 1's markers are red spheres, player 2 has blue cubes. The aim is to create a line of four markers, all of the same type, along the x-, y-, or z- axes, or the diagonals across the XY, XZ, or YZ planes, or from corner-to-corner.

The non-networked FourByFour game described in this chapter is a simplified version of a game available in the Java 3D distribution.

The main programming features of FourByFour are:

• the use of parallel projection so that the poles and markers at the back of the scene do not appear smaller than those at the front;
• the use of Switch nodes to hide the red and blue markers on screen until they are required by a player;
• a PickDragBehavior class that allows a player to select a position by clicking with the mouse, and to rotate the game board via mouse dragging;
• another example of picking, somewhat simpler than those in the Shooting and Fractal landscape examples (Chapters 23 and 26).

The networked version of FourByFour, called NetFourByFour, is an instance of a threaded client and server, similar in style to the threaded Chat application of Chapter 30. However, there are additional requirements for a networked two-person game, including the need to order the players' turns, and to control the number of players involved.

The main contribution of NetFourByFour is to illustrate strategies for designing and implementing networked two-person games:

• the development of the application in two stages, as mentioned above;
• the use of network protocol diagrams to specify the interactions between the clients and server;
• the use of UML activity and sequence diagrams to trace turn-taking from one player, through the server, to the other player.

The NetFourByFour GUI also extends the Canvas3D class to place overlays on-screen.

Downloads

• The PDF file for the draft chapter (the old ch.20) (584 KB). Last updated: 7th July 2003.
  
• Zipped Source code (33 KB). Last updated: 20th April 2005. The book's code.
  

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• Back to Chapter 30. Network Chat
• On to Chapter 32. Networked Tour3D