[comp.sys.amiga] glitching sprites while doing ScrollVPort

karl%sugar.uu.net@UDEL.EDU (10/04/88)

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From: Karl Lehenbauer <karl@sugar.uu.net>
Subject: glitching sprites while doing ScrollVPort
Message-ID: <2716@sugar.uu.net>
Date: 30 Sep 88 22:47:55 GMT
Organization: Sugar Land Unix - Houston, TX
To:       amiga-relay@UDEL.EDU
Sender:   amiga-relay-request@UDEL.EDU

I'm having some problems with a little technology demonstrator I'm cooking
up.  It is a lunar lander that vertically and horizontally scrolls a
320X200 screen over a 640X400 IFF ILBM using ScrollVPort.  The problem is
that when the screen is scrolling, the sprites glitch, show as vertical
crud for the whole height of the display and such.  I was wondering if
anybody knows offhand what I should be doing that I'm not.  It's possibly
just a dumb bug inside the program, though, 'cuz it's kind of hacked, but
it's so strongly correlated with the scrolling, I thought there might be
something I missed.
--
-- "Insert the disk at your own risk."  -- Firesign Theater
-- uunet!sugar!karl, Unix BBS (713) 438-5018

karl%sugar.uu.net@UDEL.EDU (10/04/88)

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From: Karl Lehenbauer <karl@sugar.uu.net>
Subject: Re: glitching sprites while doing ScrollVPort
Message-ID: <2724@sugar.uu.net>
Date: 2 Oct 88 00:47:41 GMT
Organization: Sugar Land Unix - Houston, TX
To:       amiga-relay@UDEL.EDU
Sender:   amiga-relay-request@UDEL.EDU

[I curse the day I first started using an overscan Workbench]

In article <6084@pasteur.Berkeley.EDU>, koster@cory.Berkeley.EDU (Anonymous
 user) writes:
> The symptoms you describe (tall vertical lines, garbage sprites that come
> in and out) are exactly the ones I found when someone had his preferences
> display position way to the left, and was running a program that used
> sprite 5. That was REALLY fun to debug! I just assumed it was my fault, and
> just couldn't find the bug.

Bingo.  I shifted the screen to the right with Preferences and the problem
went away.  Whew, thanks to sub-24-hour news turnaround, I didn't burn too
much time on this honker.
--
-- "If it's soft and hard to find, it's wimpy!"  -- Wimpy's Software
-- uunet!sugar!karl, Unix BBS (713) 438-5018