问题
All I know is that delta relates somehow to adapting to different frame rates, but I'm not sure exactly what it stands for and how to use it in the math that calculates speeds and what not. Where is delta declared? initialized? How is it used? How are its values (min,max) set?
回答1:
It's the number of milliseconds between frames. Rather than trying to build your game on a fixed number of milliseconds between frames, you want to alter your game to move/update/adjust each element/sprite/AI based on how much time has passed since the last time the update method has come around. This is the case with pretty much all game engines, and allows you to avoid needing to change your game logic based on the power of the hardware on which you're running.
Slick also has mechanisms for setting the minimum update times, so you have a way to guarantee that the delta won't be smaller than a certain amount. This allows your game to basically say, "Don't update more often than every 'x' milliseconds," because if you're running on powerful hardware, and have a very tight game loop, it's theoretically possible to get sub-millisecond deltas which starts to produce strange side effects, such as slow movement, or collision detection that doesn't seem to work the way you expect.
Setting a minimum update time also allows you to minimize recalculating unnecessarily, when only a very, very small amount of time has passed.
回答2:
Have a read of the LWJGL timing tutorial found here. Its not strictly slick but will explain what the delta value is and how to use it.
来源：https://stackoverflow.com/questions/8282501/how-do-i-work-with-delta-in-slick2d-lwjgl-or-game-programming-in-general