Farseer Physics non-XNA on separated thread

Question

I'm developing a game in C# with Farseer Physics without XNA. I put world.Step(float dt) in a separated thread in order to keep the form alive (in fact, a while loop would block every other operation). Well, the ball, a dynamic body, runs faster or slower depending on CPU frequency I think. I thought about Thread.Sleep() with a delay time calculated by reading the CPU frequency and mutiplying it by something, but I'm pretty sure I'm wrong. I'm a little noob. Any suggestion?

Answer 1

Thread.Sleep is very much not an accurate way to time things. You want to use something like:

Stopwatch timer = new Stopwatch();
timer.Start();

Which you can then use to drive a timed update loop like this:

// Run enough updates to catch up to the current time
private void Idle()
{
    double time = timer.Elapsed.TotalSeconds;
    accumulatedTime += (time - lastTime);
    lastTime = time;

    const double frameTime = 1.0/60.0; // 60 frames per second
    while(accumulatedTime > frameTime)
    {
        world.Step((float)frameTime);
        accumulatedTime -= frameTime;
    }
}

You can then call the above Idle method followed by a short Sleep in a loop.

Or you could just call it from an event handler for Application.Idle - either directly on the UI thread, or by signalling your other thread.