这个机制的加入 比 AS3好了很多

AS3的EnterFrame相当于UNITY的Update

但是FLASH做不了也是因为浏览器的限制吧!

Here's how the fixed time step is calculated. Before every frame is drawn onscreen, Unity advances the fixed time by fixed delta time and performs physics calculations until it reaches the current time. This directly correlates to the Fixed Timestep property. The smaller the value of Fixed Timestep, the more frequently physics will be calculated. The number of Fixed frames per second can be calculated by dividing 1 by Fixed Timestep. Therefore, 1 / 0.02 = 50 fixed frames per second and 1 / 0.05 = 20 fixed frames per second.

以下是固定时步如何计算。在每一帧图像绘制到屏幕之前，Unity将固定时间加上固定时步，然后执行物理计算，直到它到达当前时间。该过程与固定时步属性直接相关。固定时步值越小，物理计算就越频繁。将1除以固定时步可以得到每秒计算固定帧的数量。所以，1 /0.02=50固定帧每秒，1 /0.05=20固定帧每秒

http://www.ceeger.com/Components/class-TimeManager.html