It seams that all particleSystems in a .babylon scene file is automaticly started.   ParticleSystem.Parse = function (parsedParticleSystem, scene, rootUrl) { ..... particleSystem.start(); ....... };   This is great, BUT.....sometimes we do NOT want all the particleSystems to start when the scene loads! So we should add an option to the particleSystem: In function ParticleSystem(name, capacity, scene, customEffect) { ..... this.autoStart