How To: Make a Game Use a Variable Time Step
The Complete Sample
The code in this tutorial illustrates the technique described in the text. A complete code sample for this tutorial is available for you to download, including full source code and any additional supporting files required by the sample.
To Make a Game Use a Variable Time Step
- Create a class that derives from Game.
-
Set IsFixedTimeStep to false. This causes Update to be called as often as possible instead of being called on a fixed interval.
this.IsFixedTimeStep = false;
-
Since the amount of time between calls to Update will vary, specify any rates used in the game as units per millisecond (ms).
// Speed in world units per ms. private double speed = 0.02f;
-
In Update get the value of gameTime.ElapsedGameTime.TotalMilliseconds. This gives the amount of time that has passed since the last call to Update.
// Time elapsed since the last call to update. double elapsedTime = gameTime.ElapsedGameTime.TotalMilliseconds;
-
Determine the change that occurred since the last update by multiplying any rates being used by the elapsed time.
// Multiply speed by elapsed time to get the distance moved. double distance = (speed * elapsedTime);
