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Demos Amiga Demoscene Archive Forum / Coding / Vertical stripe bug (mouse cursor sprite perhaps)?

 

Author Message
sdw
Member
#1 - Posted: 14 Jul 2013 12:31
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I'm coding on a little intro for OCS. Sometimes when I start it, I get a vertical stripe going from top to bottom over the entire screen. A reasonable guess would be that it is a sprite, and it seems like it appears where I have the mouse cursor in the Amiga DOS screen before I start the intro, so that further strengthens the suspicion.

Obviously I have missed some kind of "disable sprites" stuff in my init code - what's the easiest way to do it to avoid bugs like these?
DrCinicus
Member
#2 - Posted: 14 Jul 2013 15:16
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When you disable the sprite DMA, you have to wait the beam position is outside the visible video, IIRC over line 300, otherwise you obtain a vertical strip for every sprite on the video: in this case the mouse pointer (Sprite 0).

Bye
sdw
Member
#3 - Posted: 15 Jul 2013 00:17
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Thanks, added a VBL wait before the code that messes with DMACON (haven't written the init code myself...) - let's see if that solves it!
noname
Member
#4 - Posted: 16 Jul 2013 14:36 - Edited
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Waiting for VBL is good. For more background infos check How to Code 7 and maybe also their FixSpritesSetup routine from startup.asm.

 

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A.D.A. Amiga Demoscene Archive, Version 3.0