public class ParticleEmissionModule
extends java.lang.Object
粒子系统分组,发射率,指定时间内发射多少个粒子,越多会越密集
但不会超过最大粒子数量
Particle system grouping, emission rate, specifies how many particles are emitted in a given time, the more the denser
but will not exceed the maximum number of particles