许多自然现象是由很多小的小颗粒组成的，它们有相似的行为。（例如，雪花落下，闪烁的火焰，冲出枪管的“子弹”），粒子系统用来模拟这种现象-Many natural phenomena is caused by many small, consisting of small particles, they have similar behavior. (For example, snowflakes fell, flashing flame,