Thread: Synchronizing time step.

  1. #1
    Registered User
    Join Date
    Apr 2009

    Synchronizing time step.

    Hello guys.

    Is my first post here. I'm having problems with time step.
    I'm using a physics engine that I have to tell how much times it will update each second, but my program is running at inconstant rate.

    Have some way to force the main loop to spend a specific amount of time each pass?

  2. #2
    Officially An Architect brewbuck's Avatar
    Join Date
    Mar 2007
    Portland, OR
    Quote Originally Posted by Auradrummer View Post
    Have some way to force the main loop to spend a specific amount of time each pass?
    Yes, I have a way of forcing any piece of code to execute in any arbitrary length of time. I used this to predict the final outcome of the universe in less than two microseconds.

    More seriously, you need to occassionally call a time-getting function to see if you're getting too far "ahead", sleeping if necessary. For instance, if each loop iteration takes dt seconds, then:

    double t = CurrentTime();
        if( t > CurrentTime() + slop )
            WaitUntil( t );
        t += dt;
    Where CurrentTime() gives the current time in seconds (double precision), slop is the maximum time you are allowed to overshoot (possibly 0.0), and WaitUntil() is a function which causes the program to sleep until the time is greater than or equal to t.
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);

  3. #3
    Registered User
    Join Date
    May 2007
    Good physics engines have ways to deal with this common problem.

    Typically, you either have an interpolation (if your a bit slow), or the engine 'cycles twice' (or more) for it's fixed timestep to catch up.

    Bullet, for example, offers a fairly standardized approach - but each engine can have different service for this, and you'll need to check documentation / example programs.

Popular pages Recent additions subscribe to a feed

Similar Threads

  1. Replies: 26
    Last Post: 07-05-2010, 10:43 AM
  2. Representing floats with color?
    By DrSnuggles in forum C++ Programming
    Replies: 113
    Last Post: 12-30-2008, 09:11 AM
  3. Sending an email in C program
    By Moony in forum C Programming
    Replies: 28
    Last Post: 10-19-2006, 10:42 AM
  4. calculating user time and time elapsed
    By Neildadon in forum C++ Programming
    Replies: 0
    Last Post: 02-10-2003, 06:00 PM