Changes the current particle emitter speed factor.
#ParticleEmitter The particle emitter to use. Factor The new particle emitter speed factor. The default speed factor is 1. When using a value greater than 1, then the emitting speed will be increased. When using a value lower than 1, then the emitting speed will be decreased. For example, using a speed factor of 4.5, will have the particle emitting speed multiplied by 4.5. Using a speed factor of 0.5, will have the particle emitting speed divised by 2.