Pseudo Vertical Scrolling Demo - "The Art of Scrolling Without Scrolling"

[+SmittyB]

I was asked recently about vertical scrolling for a shooter on the 7800. Of course this isn't a straightforward thing to do, so as usual I thought I'd bring up the old idea of drawing a static object on the screen and then scrolling the graphics memory in RAM.

This isn't by any means the best example simply because I didn't want to spend too long on a throwaway demonstration, but it should give people an idea of how to go about it. I call it "The Art of Scrolling Without Scrolling".

 

Demo running on raz0red's JS7800

 

 

TheArtOfScrollingWithoutScrolling.zip TheArtOfScrollingWithoutScrolling.bas.a78

[RevEng]

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bravo!!! ?

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[+Pat Brady]

When you say “not straightforward” are you talking about the parallax scrolling shown in your demo (an impressive effect!), or vertical scrolling in general?

[+SmittyB]

I mean the typical method on the 7800 of changing the zone sizes and then using an interrupt to fiddle with graphics offsets. As 7800BASIC sits right now I don't think there's a way to implement it with games using that.

 

This method let's you not only scroll the whole screen if you want but individual parts of it as you see in the demo, and the same ideas can be applied to horizontal scrolling, fade effects, or plenty of other nifty tricks.

[+mksmith]

Really clever stuff @SmittyB - thanks for sharing ?

[+Muddyfunster]

That's really cool @SmittyB, reminds me of a shoot em up (name escapes me) where you are flying down a canyon. The effect is really nice.

 

 

[willbilly]

Now this seems like one of those advantages over the NES/SMS that would have really wowed customers back in the day.

[SlidellMan]

Thanks for giving me the inspiration to re-write my game on account of my original main file getting too cluttered and possibly bloated.

[+SmittyB]

8 hours ago, SlidellMan said:

Thanks for giving me the inspiration to re-write my game on account of my original main file getting too cluttered and possibly bloated.

No problems, I hope it lets you achieve what you're aiming for.