Comments on Iain Lobb: Understanding Game Time Steps - Your 3 Options

2010-08-02T13:55:55.586+01:00

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Thanks for your input Al. After Mike and your grea...

2010-07-29T18:54:41.557+01:00

Thanks for your input Al. After Mike and your great contributions I think I will definitely take another look at delta time.

Fix your timestep also syncs with real time by the way, even if the CPU slowed right down to 1 fps, so that would have also stopped your cheats (and probably crashed their computer). Competitions shouldn't rely on client-side logic anyway as Flash is too easy to RAM hack etc.

Option 1 is essential option 2 with a deltaTime of...

2010-07-29T13:23:16.843+01:00

Option 1 is essential option 2 with a deltaTime of 1. Using the deltaTime is really the only way to keep Flash game responsive.

Gaffers technique is great - but you must remember we have 1 thread in Flash and if we sit in a while loop (or multiple in the final method) for longer than the number of MS for a frame we end up in with a non-responsive game - as you mention.

By using deltaTime we are not limited to a Euler integrator, which as Mike says, is generally enough for simple games. For rigid-bodies, springs and so on we can use Runge-Kutta, LeapFrog (Velocity Verlet) and so on to perform each step. This keeps things from exploding due to inaccuracies.

Furthermore if you ever add a high-score to your game based on a timer, you must use deltaTime as there are tools to slow the CPU for cheating. As we found out on a certain soft-drink site.

Great site btw!

FWIW, I've found that option 2 with plain Eule...

2010-07-27T02:44:10.975+01:00

FWIW, I've found that option 2 with plain Euler integration is actually very safe for most games. You start running into problems only when a) your framerate varies wildly or b) you are trying to have very realistic physics. I've been getting away with it so far anyway :)

You an also use this trick to avoid the worst of Euler integration: http://www.niksula.cs.hut.fi/~hkankaan/Homepages/gravity.html