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Old 20 October 2021, 16:56   #1
AndyJF
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Weird effect when scrolling

I'm trying scrolling effects for the first time but getting a strange ripple / flicker. You can see it here

[ Show youtube player ]

In each program loop, I use screen copy to move the whole screen down by 1 pixel then paste what was the bottom line of pixels back at the top, but as you can see it's not a smooth effect. I've tried using Def Scroll but it's exactly the same. I am using double buffer.

Thanks

Setup - WinUAE 4.4.0, Windows 10, AMOS Pro V2
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Old 20 October 2021, 18:07   #2
rothers
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Do you have a waitvbl?

I have a vague memory of a plugin for amos which gave far faster scrolling blits for this function.
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Old 20 October 2021, 19:25   #3
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Yeah I've got a wait vbl
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Old 20 October 2021, 21:14   #4
Retro1234
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Probably too bigger area for screen copy, screen copy was a terrible way to scroll a screen use hardware scrolling with the Screen Offset command.
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Old 21 October 2021, 11:59   #5
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Screen offset works perfectly, thanks!

[ Show youtube player ]
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Old 21 October 2021, 18:36   #6
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Looks like your vertical scrolling tiles.
Idrougge kindly shared some code to endlessly hardware scroll vertically with tiles in Amos, it might be useful

http://eab.abime.net/showthread.php?t=80646

Last edited by Retro1234; 22 October 2021 at 09:43.
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Old 22 October 2021, 09:56   #7
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Thanks for the link, I'll take a look
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Old 22 October 2021, 12:27   #8
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Amos not including a built-in solution to scrolling was a disaster.
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Old 22 October 2021, 18:49   #9
Retro1234
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it does Screen Offset ?
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Old 22 October 2021, 19:29   #10
rothers
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Quote:
Originally Posted by Retro1234 View Post
it does Screen Offset ?

It has no (tile) scrolling engine though.


So it's a fiasco to figure out the best way to do it.


If you go about it wrong it's hopelessly slow (but the manual gives no indication of the right/most optimised route).


I still could not tell you the fastest way to do it in AMOS.


You just end up with games using the max screen size and hacks.
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Old 22 October 2021, 19:34   #11
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Same as every Amiga language but what still baffles me is examples back in the day, like with Tome telling people to use screen copy for scrolling, we know now this wrong but why they endorsed this? anyone have any idea?
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