Particle Systems

A very large number of phenomena can be modeled accurately or approximately as particle systems. Fireworks, fountains, explosions, shoals of fish, gasses, stars etc. They all work in a similar way.

A particle system consists of a collection of objects with various properties, and some behavioural laws they must obey. Exactly what those properties and laws are depends on what you are trying to model. Some particle systems may need many properties and complex laws, while others may be extremely simple.

In this page I will explain some of the basic ideas behind particle systems, and the next few pages will go into more detail about specific peoperties and behaviours.
Particle smoke simulation.
1024 anti-aliased particles.

Properties: What every particle needs

Each particle will need some properties to set it apart from all the other particles. In general all particles in a syatem will have the same collection of properties.

Here are some examples of typical properties given to particles.

Position: Where the particle is.

Every particle system that deals with moving particles will need to keep track of the position of each particle. 2 dimensional systems will need 2 co-ordinates (X, Y). 3 dimensional systems will need 3 (X, Y, Z).

Velocity: Speed and direction

With position tends to come velocity. Velocity is a vector which tells the system how fast and in what direction the particle is moving. Each time step, the velocity is added to the position to move the particle.

Acceleration:

In the same way velocity affects position, so acceleration affects velocity. The acceleration of a particle is usually due to a force acting on it. This force is often gravity, or an attraction or repulsion to other particles.

lifespan

Frequently, because of computing power restraints, particles are given a limited lifespan. Older particles are removed after a certain length of time to make way for newer particles. You may want particles such as sparks from an explosion to burn out after a few seconds, in which case, their brightness and colour would also change over time.