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From 40 Raster Lines to 1

Posted on

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.


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

If you really want to help get Parallaxian finished, kindly support the continuation of its development via one of the options below, so that I can devote the necessary time to it; it's a truly huge project and although the toughest technical challenges have been completed, there remains a lot of hard work to get it over the finishing line.

Way #1: Start Your Amazon Sessions via (Costs You Nothing!)

This one should be the easiest because it's a painless and indirect way to help me for something you would be doing anyway, regardless of my request for help.

So how does it work?

Well, it makes no difference what you're buying on Amazon... whether it's a garden gnome for your dad, jewellery for your wife, the new C64 Maxi for yourself or an obscure first edition by an even more obscure 17th century Belgian poet for someone you very much dislike.

The point is, if you buy anything on Amazon, even your groceries, I will automatically receive a commission as long as your Amazon session begins as a click on an Amazon product banner on this website or just on any generic Amazon link on this website (such as those listed below):

So, you would make your daily visit to to check out what's new and then, while you're here, enter Amazon via one of those links to order whatever you were planning on buying anyway, thus doing your bit to advance Parallaxian's development.


Way #2: Purchase Merch from the Kodiak64 Shop

Hosted externally (for now) on Teespring, the Kodiak64 shop features limited edition C64-related merchandise, for which I have mostly set my margin at 15% of the retail price (to keep it as low as worthwhile).

6502 LOVE

I intend to change designs every month to keep things fresh, albeit with the core themes remaining Commodore 64 centric.

Way #3: PayPal Donation

Finally, at the highest rung of the altruism ladder among the 3 options, maybe 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).

Help Kodiak64 for FREE!

Click here to read how.

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Kodiak64 Newsletter

100% free, 100% spam-free!

(You can view a sample here).