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Help => Graphics => Topic started by: slotdev on May 23, 2012, 02:38:01 pm

Title: framerate limit
Post by: slotdev on May 23, 2012, 02:38:01 pm

Hi Folks

Can someone sanity check me with this statement?

I do not have to call sf:Sleep anywhere in my program IF I call SetFramerateLimit already?

Currently, I call sf:Sleep(3) after every check of the render loop (no matter if we rendered something or not).

Thanks
Ed

Title: Re: framerate limit
Post by: Laurent on May 23, 2012, 02:40:19 pm

Quote

I do not have to call sf:Sleep anywhere in my program IF I call SetFramerateLimit already?

Correct, SetFramerateLimit already calls sf::Sleep to keep a constant framerate.

Title: Re: framerate limit
Post by: slotdev on May 23, 2012, 03:07:24 pm

Hmm OK. Well removing a sleep(3) from my program has really increased the framerate.....but now CPU is at 99% :(

Title: Re: framerate limit
Post by: Laurent on May 23, 2012, 03:08:21 pm

What's your framerate without calling SetFramerateLimit, and what limit do you use?

Title: Re: framerate limit
Post by: slotdev on May 23, 2012, 03:20:05 pm

I think the problem is we have our own framerate control, and also that in SFML. Let's assume we use 30fps.

We use a timer and we check this against the amount of time the last render took (so if render took 8ms, we will start rendering again in 25ms). This is called in the game loop.

SFML (I guess) does something similar, but did you mean it so we call Draw(etc) and then Display() as often as possible, and SFML won't update the screen if it's not time yet?

I hope that makes sense :S

Title: Re: framerate limit
Post by: Laurent on May 23, 2012, 03:29:47 pm

SFML does exactly what you do, ie. waiting in display() until the requested frametime is reached. So there's no point activating both :)

Title: Re: framerate limit
Post by: slotdev on May 23, 2012, 03:42:27 pm

Quote from: Laurent on May 23, 2012, 03:29:47 pm

SFML does exactly what you do, ie. waiting in display() until the requested frametime is reached. So there's no point activating both :)

Ah ha. The difference is then, that we continue to do other code which is required (checking other events/attached peripherals/etc) in between each render. So maybe disable the SFML framerate checking would be a good idea....

Title: Re: framerate limit
Post by: atlasC1 on June 05, 2012, 06:41:44 am

I'm brand new to SFML (trying it out in comparison to Allegro 5), and I too am slightly confused about the frame rate limiting.

Does limiting the frame rate limit the entire game loop speed? Or will it only affect the loop when display() is called?

What happens if our game runs into a complex situation, and the update takes too long to fit into a 60 ticks per second loop. Does the loop automatically drop frames, or will it continue to render them and slow down the loop even more? Would it be better to control the timing manually in this case, instead?

Thanks, and excellent work with the library!
-atlas

Title: Re: framerate limit
Post by: Laurent on June 05, 2012, 07:57:30 am

A few lines of code may be clearer than a long explanation:

void Window::display()
{
    ...

    if (m_frameTimeLimit != Time::Zero)
    {
        sleep(m_frameTimeLimit - m_clock.getElapsedTime());
        m_clock.restart();
    }
}

There's really nothing complicated behind this feature, it's exactly what you would write if you did it yourself.

Title: Re: framerate limit
Post by: atlasC1 on June 06, 2012, 04:34:56 am

Thanks Laurent,

Makes sense; I took a look at the implementation in window.cpp.

So, to my understanding, by using this option, your game loop rate becomes dependent on your frame rate.

-atlas

Title: Re: framerate limit
Post by: Tank on June 06, 2012, 11:00:00 am

Yes, but nothing stops you from making your calculations dependant on time. ;)