Posted By
Mad
on 2021-08-17
13:50:53
|  Re: AROK 2021...
@Doug: This is most probably the famous "Censor Color Ram Scrolling" (as I would call it).. Similar effects are used since "ages". Key is to just update the color ram. For many of these are several flipped bitmaps (the grid) involved to get the thing animated on a fluid per pixel basis and not just the "harsh" colorram blocks.
There was some demo back some years where they started to scroll the bitmap (whilst animating the colorram), so the bitmap is fine scrolled (to the right) and the colorram moves (to the left), by this you get a pretty decent wobble effect onto screen. Say you scroll the bitmap 7 pixel to the right, and it seems it scrolls visually actually 1 pixel to the left, because you scrolled the colorram (8 pixel to the left), too. And it seems that it wobbles :).. Let me search that particular demo.. https://www.youtube.com/watch?v=X6RDZ__10qw (At least that's how I would do this effect in this demo. Dunno if it is really that way.)
However this one seems a bit different. Mainly because it's fullscreen (bitmap scrolling on C64 would limit the display region). Could be that some other trickery is involved there too.. For most of these effects the key is to update the colorram and maybe change the bitmap address/pointer.. Maybe this one even incorporates charmode, dunno..
Maybe some guys should talk who really know of this effect in that particular demo.. 
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