Particle Emitter

Every particle system comes with a particle emitter that may be used to automatically add particles to the particle system.  You can easily specify how often new particles should be added to the particle system by setting the particle system emitter's ParticlesPerSecond property.  The emitter also comes equipped with Position3D, Orientation3D, and PivotPoint3D properties that are updated automatically each time the particle system's Update() function is called.  So unlike the particles who need to have their position and orientation explicitly updated each frame by using particle events, the emitter does not.  Also, when new particles are added to the particle system, if the emitter is moving very fast or the frame rate drops for some reason, then many particles would typically be released in one location (i.e. the emitter's new location) when really they should be spread out between the emitters old location and the new one.  To avoid this, the particles are spread out using linear interpolation between the emitter's old position and its new one.  The orientation of the emitter is treated similarly using spherical linear interpolation for the similar case that the emitter is rotating very fast.