M3G Chapter 5.   The Beginnings of a FPS

[ This chapter does not appear in the book. ]

It's time to track down those penguins from earlier chapters and treat them with extreme prejudice.

GunnerM3G is a simple FPS (First-Person Shooter), where you roam about looking for two penguins to shoot at. Once a penguin's been blasted three times, it disappears from the scene. Each time you fire the gun, there's a flash of light and a pleasing laser beam-like noise. If the gun's pointing at a penguin, they're enveloped in a nasty looking animated fireball, accompanied by an explosion sound.

The pictures on the right show the user amongst the penguins, moving in on one of them and testing the gun, and finally blasting away.

The new programming elements in GunnerM3G:

• The camera has two 2D images attached to it. The "gun hand" is permanently visible, while the "shot flash" appears briefly after the user presses the fire key.
   
  
• We shoot a pick ray into the scene and obtain a reference to the object that it hits. If it's a penguin then an explosion occurs at the intersection point. The ray is a M3G level construct, not a 'death' ray.
   
  
• The explosion is a series of 2D images. An image briefly becomes the texture for a square mesh, before being replaced by the next image in the sequence.
   
  
• This example supports layered sounds, where multiple laser blasts and explosions can be heard together.
   
  
• A penguin mesh contains a PenguinInfo object as its user object, which allows us to store extra details in the mesh, such as the number of 'lives' the penguin has left.

A guiding principle is to fake the 3D effects as much as possible. The "gun hand", the "shot flash", the explosions, the floor, and the background are all 2D visuals wrapped over simple rectangular meshes. Only the penguins are complicated models: they must have 3D depth, since the user can move around them.

Readers may recognize some elements from earlier chapters. The camera controls are based on those from the MobileCamera class, but we've (mercifully) dispensed with modes. The camera only moves forwards, backwards, and turn left or right. The floor is a tiled texture, created using TiledFloor from M3G chapter 4.

A final touch is that the penguins are randomly positioned on the floor each time the MIDlet begins, and the floor and background images are randomly chosen from a small selection of alternatives. The image on the right shows another execution of GunnerM3G.

There are numerous ways GunnerM3G could be improved. One of them is to add actual laser beams (or bullets, or whatever). Although the visuals include a "shot flash" and an explosion, there's no representation of the shot itself.

Downloads

• The PDF file for M3G Chapter 5 (337 KB). Last updated: 4th December 2004.
  
• Zipped Source code for M3G Chapter 5 (155 KB). Last updated: 4th December 2004.
  

• Up to the Killer Game Programming in Java Index Page
• Back to M3G Chapter 4.5. Using M3G File Models
• On to M3G Chapter 6. Dynamically Textured Billboards

Dr. Andrew Davison
E-mail: ad@coe.psu.ac.th
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