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From 40 Raster Lines to 1

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By Kodiak


If you've read my tech article, Bank-Switched Scrolling, you will remember how I had to find a way to compress Parallaxian's scroll code for the distant mountains in the parallax landscape down from the original approximately 40 raster lines, and ended up getting it squeezed into a much more compact 9.

That was achieved using double-buffering to spread the time-consuming software (char) scrolling over several screen frames of hardware scrolling (a full explanation is in the article).

Bank-Switched Leapfrog Scroll Method

However, after musing upon comments from another coder on my recent article, Wild Wood Deconstructed, I thought it would be possible to have Parallaxian's main loop do the heavy lifting of the double-buffer scrolling when the interrupts are idle.

Sure, it's not an ideal solution for every layer of the parallaxed landscape, and yes, the main loop is filling up with more and more tasks, but for now there is enough cumulative interrupt idle time spread across the frames consumed between char scroll events for that slowest scrolling layer to allow the char-shifting components of its double-buffering to be removed from the interrupt schema altogether.

Ultra compressed layer 1 scroll


This was done, of course, with one eye on a possible NTSC version of the game, most likely to manifest in the form of the planned native Commodore 128 version, which may come in both NTSC and PAL flavours... subscribe to my 100% free NEWSLETTER to be kept up to date on this.

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PS: Don't forget to check the home page regularly for more articles like this and visit the Everything64 Forum to comment further.

And of course, kindly follow me on Twitter and subscribe to my YouTube channel!

Help Make Parallaxian Happen

PayPal Donation


I would ask you if you could consider a small, recurring monthly donation (and depending on your tax situation, you might even be able to designate it as a charitable donation rather than let the taxman have it).

And don't worry, you can cancel at any time... but in the meantime, it would be a welcome contribution, however petite.

Oh, and as a special thank you, all who do this will be credited in the game (unless you opt out of it if you have the same kind of incognito hermit tendencies I do).



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