Limit while loop to run at 30 "FPS" using a delta variable C++

Question

I basically need a while loop to only run at 30 "FPS". I was told to do this: "Inside your while loop, make a deltaT , and if that deltaT is lesser than 33 miliseconds use sleep(33-deltaT) ."

But I really wasn't quite sure how to initialize the delta/what to set this variable to. I also couldn't get a reply back from the person that suggested this.

I'm also not sure why the value in sleep is 33 instead of 30.

Does anyone know what I can do about this?

This is mainly for a game server to update players at 30FPS, but because I'm not doing any rendering on the server, I need a way to just have the code sleep to limit how many times it can run per second or else it will process the players too fast.

Answer 1

You basically need to do something like this:

int now = GetTimeInMilliseconds();
int lastFrame = GetTimeInMilliseconds();

while(running)
{
    now = GetTimeInMilliseconds();
    int delta = now - lastFrame;
    lastFrame = now;

    if(delta < 33)
    {
        Sleep(33 - delta);
    }

    //...
    Update();
    Draw();
}

That way you calculate the amount of milliseconds passed between the current frame and last frame, and if it's smaller than 33 millisecods (1000/30, 1000 milliseconds in a second divided by 30 FPS = 33.333333....) then you sleep until 33 milliseconds has passed. Has for GetTimeInMilliseconds() and Sleep() function, it depends on the library that you're using and/or the platform.