random spike in delta time

Question

The title pretty much sums it up. I'm using delta time to move my objects and every few seconds the delta time will spike and all the objects will jump forward. Should I just Interpolate the delta time to eliminate spikes, I don't want to do this because it could cause other problems but it could be a solution

Answer 1

It might help if you'd post a simple code example demonstrating the problem, but I'm going to take a wild guess and suggest that your time resolution is too low.

In particular, consider what happens if your simulation loop takes, say, 0.02 seconds to run, but your timer only counts whole seconds. So, for 49 out of 50 loops, the delta time you'll calculate will be exactly zero, and so the simulation time will not advance — but then the timer ticks over, the delta time becomes 1 second, and the simulation loop suddenly goes "Oh, wow, that last iteration sure took a long time! I'll have to use a huge time step to catch up!"

The best solution is simply to use a more precise time source. However, if you really can't get the time resolution you want (or if something else is causing unavoidable jitter in your loop timings), you can stabilize the timing prediction by averaging the delta time over several iterations, i.e. instead of doing this:

var baseTime = getCurrentTime();
while ( running ) {
    var currentTime = getCurrentTime();
    var deltaTime = currentTime - baseTime;
    baseTime = currentTime;
    simulate( deltaTime );
}

you could do e.g. this:

var baseTime = getCurrentTime();
var timeQueue = new Queue ();
while ( running ) {
    var currentTime = getCurrentTime();
    timeQueue.push( getCurrentTime() );
    if ( timeQueue.length > 10 ) {
        baseTime = timeQueue.shift();
    }
    var deltaTime = (currentTime - baseTime) / timeQueue.length;
    simulate( deltaTime );
}