Controls whether the Particle System uses an automatically-generated random number to seed the random number generator.
If set to true, the Particle System will generate a new random seed each time it is played. If set to false, ParticleSystem.randomSeed will be used instead, allowing for a constant seed (useful if you want your particles to play in exactly the same way each time) or user-defined random value (for example, you may want to cycle through an array of seeds).