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From: Martin Kift <M.H.Kift@swansea.ac.uk>
To: blitz-list@helsinki.fi
Date: Thu, 4 Aug 1994 09:09:13 GMT0BST
Subject: Re: Problems with blitting blocks fast enough for HW scroller
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> The problem seems to be that "block" doesn't blit to the screen
> fast enough. I'm trying to blit 20 blocks across the bottom of the
> screen (just out of view), and across the top of the screen (again
> just out of view. I'm therefore trying to blit 40 blocks at once.
Sounds painful to me.
> When the scrolling is going, there is a very very minor jerk,
> (hardly noticeble, but I can see it, and I don't like it!). This
> doesn't occur if I blit only 18 blocks on top and bottom (36 in
> total).
> I could just reduce the width of my displayed screen by 32
> pixels, but would like full screen (and even overscan if possible),
> but "block" isn't fast enough.
You are painting off the visible screen are you? Well you'd have to,
to get smooth pixel scrolling. If not, just allocate a bitmap bigger
than the visible screen by 2 16pixel blocks in all directions, and
blit into the furthest 16pixel area.
> What I would like to know is this: Is there an even faster
> blitting command than block??
> How have other people got around this problem??
If scrolling at 16pixels per frame is what you want, you don't have
much choice really. However, if 16 pixels every 2 or 4 frames is okay
(and thats still pretty fast), why not break down the bits into
groups. So, if going at 16 pixels every 4 frames, break down the
blits into equal sizes of 4 groups of blits. Save heaps of time.
Theres are more clever ways in which to do 8way scrolling, which I'm
