Watching Splitter (C64)

So last week I burbled on a little about Beyond Force’s Charlatan and mentioned in passing it’s sort-of-sequel Splitter, developed by TNT and released in early 1989, soon after Solomon’s effort. The effect in this one is even more kaleidoscopic than its predecessor and is one of those demos that can be watched for an age without realising how long you’ve been staring at the screen.

Whilst talking to Daniel “DeeKay” Kottmair about this demo and Charlatan on Facebook, he referred to Splitter as being the “first 40-char FLI” routine; this threw me a little because I’d never come across the term before – that isn’t unusual since back in the day we all tended to work in something of a bubble, which is why other routines like VSP and AGSP have alternative names – and the routine has more in common with FLD than it does to FLI. Essentially it’s using the vertical scroll register to force the VIC-II to repeat the top scanline of a bitmapped screen and, because that’s a badline being replicated, cycling between all of the blocks of colour memory in the video bank – fifteen in total since the bitmap takes the relevant part of the sixteenth away – forwards and then backwards a couple of times gets all of those colours.

The colour data is all rewritten once per france to get everything moving smoothly and each byte of the bitmap data has two colours in use so there can be eighty “splits” per scanline not including the border colours. It’s bigger than Charlatan horizontally because there’s no FLI area at the left to worry about and the routine can handle a larger vertical area as well because mirroring the effect in the way TNT has done reduces the amount of colour data it needs to refresh – that trick wouldn’t work on an FLI routine because it can’t repeat colour data in the same way.

I said last time about Charlatan being a teensy bit rough around the edges due to its pioneering nature, but Splitter seems to have spent a little longer maturing and is tighter on the presentation with everything timed up neatly. With that said I do think that Charlatan is my personal favourite of the two, but they’re both worth an extended watch once in a while, not least because of the choice of JCH music.