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Flavioweb
Registered: Nov 2011
Posts: 463 |
upscroll: fast code needed.
i'm coding a fullscreen smooth up scroller.
Actually i'm using some unrolled code to use minimum amount of cycles, but i want to know if there is a well-know method to achehive best results.
Someone can point me in the right direction? |
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yago
Registered: May 2002
Posts: 333 |
There is also a way to upscroll without any CPU usage.
You set up every 8 lines an rasterinterrupt, which changes the vic-bank/characterset/screen.
The details are a bit complicated, but then you only need to scroll the colorram.
I have used it in the Drowned Church Part in FLUT.
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Flavioweb
Registered: Nov 2011
Posts: 463 |
Quote: There is also a way to upscroll without any CPU usage.
You set up every 8 lines an rasterinterrupt, which changes the vic-bank/characterset/screen.
The details are a bit complicated, but then you only need to scroll the colorram.
I have used it in the Drowned Church Part in FLUT.
i wil give a look at your work, but we are details-hungry here...
;) |
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Repose
Registered: Oct 2010
Posts: 225 |
I was going to say the same thing. I had considered this raster method to scroll quickly an 80 column screen using custom charsets. You can scroll 80 column text at 9600 baud this way. Just sayin'.
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Bitbreaker
Registered: Oct 2002
Posts: 508 |
@flavioweb
no need to trigger an irq each 8 lines, it would most likely also be enough to start copying late enough so that you don't overtake the raster with your copy action (and cause a glitch by that). Just start at let's say $80 first and in case decrease or increase that value, until things look okay. Then you have all the remaining rastertime free in one block.
The other solutions are of course also doable and need way less rastertime, but have a bigger memory footprint. So it is up to you what is needed more :-) |
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yago
Registered: May 2002
Posts: 333 |
Yes, iirc, the 8th-line upscroller requires 16k alone for the bitmap. Some memory left here and there for sprites, but using them requires more complicated irqs.
the "raw cpu" method is surely better for games
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