Re: Problem gettting a smooth continous background scroll (SDL2)

I wanted to point out something about smooth scrolling (though this is not
your particular problem), that SDL uses integer positions and so doesn't
support subpixel positioning.  If you have a low rate of scrolling, like on
the order of 10 pixels per second or less, you will experience pixel-sized
jitter.

Jonny D


On Wed, Aug 17, 2016 at 1:44 PM, BenoitRen <[email protected]> wrote:

> I see several problems:
>
> -The duration of one frame when rendering at 60 frames per second is not
> 16 milliseconds, but 16.67 milliseconds (1000 / 60 = 16.67). This
> difference in timing adds up.
>
> -Every frame you insert a waiting period of 16 milliseconds. This does not
> take into account the time it takes to process one frame between the delays.
>
> -SDL_Delay is not very reliable. The operating system's scheduler might
> decide to allocate some time to another process instead of yours at the
> time you expect control back.
>
> There are two approaches you can take.
>
> One approach is using timers, which Lazy Foo' also explains in one of his
> tutorials. To solve the problem of one second not cleanly being divisible
> by 60, you can combine it with the approach explained by Aaron at Wolfire (
> http://forums.wolfire.com/viewtopic.php?f=1&t=16539). In short, it makes
> every first and second frame take 17 milliseconds, and every third frame 16
> milliseconds. Personally, I combined all of that with what Disch explained
> at NESDev (http://forums.nesdev.com/viewtopic.php?f=3&t=6107) to try to
> mitigate SDL_Delay's unreliability.
>
> The second approach is to have your program wait for vsync after rendering
> a frame. To use this, pass the SDL_RENDERER_PRESENTVSYNC flag to
> SDL_CreateRenderer's flags parameter.
>
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>
>

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