On Thursday, August 25, 2016 at 7:51:17 PM UTC-6,
mjm...@aol.com wrote:
> Mark Lemmert <mark.lemmert> wrote:
> > Michael,
> >
> > Thanks for confirming!
> >
> >
> > Do you know if there are applications where drawing during the veritable
> > blank interval would be more desirable than page flipping?
> >
> > Thinking more broadly than the Apple II hardware, I’m speculating that
> > using the vertical blank for drawing was mainly used on hardware that
> > didn’t have page flipping available.
> >
> >
> > Thanks.
> >
> > Mark
>
> Page flipping is definitely the more general approach, but in
> RAM-constrained applications, syncing to Vblank and staying ahead of the
> refresh is sometimes a necessity.
>
> For any animation that can be completed in a millisecond or two, it's
> pretty easy. If the animation requires several milliseconds, it may be
> necessary to order the updates top-to-bottom to stay ahead of the refresh.
>
> Lots of games have a large playfield but relatively small moving elements,
> so the animation can be done completely during vertical blanking.
>
> > On Wednesday, August 24, 2016 at 11:57:43 AM UTC-5,
mjm...@aol.com wrote:
> >> Mark Lemmert <mark.lemmert> wrote:
> >
> >>> But, my theory was/is that part of the problem occurring was that the
> >>> screen draw was simply too slow as evidenced by being able to see parts
> >>> of the screen in different frame states, and thus drawing in the vehicle
> >>> blank would possibly make it worse by adding delays, or at best only
> >>> solve part of the problem. Basically, if it's too slow, it's too slow,
> >>> was my thinking, and I didn't see how altering the draw timing would help that issue.
> >
> >
> >
> >>>
> >>
> >> I agree with your diagnosis.
> >>
> >> Drawing during vertical blanking is only effective when the actual drawing
> >> can stay ahead of the raster scan.
> >>
> >> If drawing is slower than display refresh, then page flipping is much more
> >> effective, and the flip can be synchronized with vertical blanking for even
> >> better results (if the additional wait is acceptable).
> >> --
> >> -michael - NadaNet 3.1 and AppleCrate II:
http://michaeljmahon.com
> >
>
>
>
> --
> -michael - NadaNet 3.1 and AppleCrate II:
http://michaeljmahon.com
Has anyone determined what size of area can be drawn within a vertical blank period?