Mail Archives: djgpp/1998/07/20/23:47:04
From: | "jakub" <marushka AT ozemail DOT com DOT au>
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Newsgroups: | comp.os.msdos.djgpp
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Subject: | Re: Sprite "ghost" help please.
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Date: | Tue, 21 Jul 1998 13:40:02 +1000
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Organization: | OzEmail Ltd.
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Lines: | 54
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Message-ID: | <6p12m0$r7u$1@reader1.reader.news.ozemail.net>
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References: | <002901bdb03d$955c7500$784e08c3 AT arthur>
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NNTP-Posting-Host: | slsdn2p08.ozemail.com.au
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To: | djgpp AT delorie DOT com
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DJ-Gateway: | from newsgroup comp.os.msdos.djgpp
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I've noticed that the allegro demo game has the same problem on my system.
I select page flipping mode, with a 640x480 screen.
When you move your shift left-right, I can see two ships slightly appart,
like a ghost image on a bad tv set. It seems I am seeing the last position
of the ship sprite.
Is this normal?
Arthur wrote in message <002901bdb03d$955c7500$784e08c3 AT arthur>...
>>I have a sprite that moves horizontally across the screen controlled by
the
>>keyboard.
>>
>>Am using Allegro, with a 640x480 screen, and page flipping.
>>The problem is that when the ship moves, I can see it 'flickering' at the
>>edges.
>
>
>You are using two "screens" do draw sprites. It may seem a stupid question,
>but are you drawing and erasing the same sprites from the same screen each
>loop. It happens.
Think I am doing it the right way, I posted a bit of my source in my
original message. I just copied the page flipping idea from one of the
allegro examples.
>Also, are you checking for a vertical blank before you
>swap the screens?
I just added this to the source but it has not made any difference.
>
>The correct order (although this can vary depending on what graphics mode
>you're in or what graphics card you have) is:
>
>1) erase old sprites on hidden screen.
>2) draw new sprites on hidden screen.
>3) wail for vertical retrace.
>4) swap screens.
Yes this is what I am doing.
>
>HTH
>
>James Arthur
>jaa AT arfa DOT clara DOT net
>
>
>
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