Particle in a discrete time physics simulation
The Particle class provides the basis for particles in a ParticleSystem simulation. The particles handle their own physics interaction calculations. You can have as many, or few, spatial dimensions as you like.
Extend this base class to add extra functionality, such as the ability to render to a graphics display (see RenderingParticle for an example of this)
Particle maintains lists of other particles it is bonded to. The bonds have direction, so the bonding information is stored in two lists - bondedTo and bondedFrom.
Bonds are made and broken by calling the makeBond(...), breakBond(...) and breakAllBonds(...) methods.
Particle calculates its interactions with other particles when the doInteractions(...) method is called. This must be supplied with an object containins the laws to apply, and another providing the ability to search for particles within a given distance of a point. See SimpleLaws/MultipleLaws and SpatialIndexer respectively. This updates the velocity of the particle but not its actual position.
The particle's position is only updated when the update(...) method is called.
A simulation system should calculate each simulation cycle as a two step process: First, for all particles, calling doInteractions(...). Second, for all particles, calling update(...).
A particle can be frozen in place by calling freeze() and unFreeze(). This forces the particle's velocity to zero, meaning it doesn't move because of interactions with other particles.
The simulation must have a 'tick' counter, whose value changes (increments) every simulation cycle. Particle stores the last tick value it was presented with so that, when interacting with other particles, it can see which others have already been processed in the current cycle. This way, it avoids accidentaly calculating some interactions twice.
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-- Automatic documentation generator, 05 Jun 2009 at 03:01:38 UTC/GMT
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