Killer Game Programming in Java

Chapter 21. Particle Systems

Particle systems are an important component of many 3D games: when you see sparks flying, smoke swirling, fireworks exploding, snow falling, water shooting, or blood spurting, then it's probably being done with a particle system. A particle system consists of a large population of individual particles, perhaps hundreds of thousands, though many commercial games use far fewer depending on the effect required. The particle system is in charge of creating and deleting particles and updating their attributes over time.

A particle is typically rendered as a graphics primitive, such as a point or line, as opposed to a full-fledged 3D shape, such as a sphere or cylinder. This means that rendering overheads can be reduced, an important consideration when so many particles are involved. However, with the advent of more powerful graphics cards, particle systems have started to utilize polygons (e.g., particles made from triangles and quadrilaterals [quads]), which allow textures and lighting to be introduced.

The attributes of a particle vary depending on the kind of system required but typically include position, velocity, forces (e.g., gravity), age, color/texture, shape, size, and transparency. The code that updates a system usually affects particle attributes using time-based equations, but other approaches are possible. For instance, a particle's new position may be a random adjustment of its previous position.

Particle systems often have a generation shape ...