Watching NWCUG Demos (C64)

As the name might suggest, the North-West Commodore User Group – or NWCUG for short – wasn’t actually a demo or cracking crew in the same way that contemporaries like the Mean Team or Borderzone were, it was instead a user group which covered, perhaps unsurprisingly, the north west of the United Kingdom. They also had a presence on UK-based online service Compunet and a few of their members produced a cluster of demos in the group’s name for release on said service so, as a “bumper” post to get back up to speed after a few weeks off, here’s a look at the three demos bearing the NWCUG brand in their name.

To begin with we’ve got The NWCUG Demo, a two parter which starts with an intro whizzing some square blocks around the screen and running a scrolling message across the bottom; nothing special but it’s fun to watch and has a good, upbeat tune playing as well. The main part has a large scrolling message at the bottom of the screen where each character in the font has been scaled up to eight times its regular size and there’s an area at the top where a series of pictures dissolve in and out. There’s also a NWCUG logo built from expanded sprites which sits in the lower border and a couple of tunes available from the function keys including a solid cover of Dire Straits’ Walk Of Life.

As with the first demo, NWCUG 2 opens with a scroller and sprite sinus, although everything has been overhauled since the previous demo’s intro; the sprites this time are defined as hearts rather than just blocks and their movements are more interesting, with the latter also being true for the excellent multi speed, direction and colour scroller which is, for me at least, only marred by the short length of the text especially since this is probably my favourite piece of music in all three of these demos as well.

Pressing the space bar will start the second part which has some Max Headroom animations originally drawn by Bob Stevenson and reworked via ESCOS to use the upper, lower and side borders whilst dancing to some appropriate David Whittaker music. A tap of the Restore key from there brings up a simulation of the NWCUG page on Compunet, accompanied by some classical music and a scrolling message where the “duck shoot” menu would usually be and, when the music ends on this part it, hands over to a simulated test card entirely built from colour splits.

NWCUG Demo 3‘s first part has some raster bars in the side borders, although sadly they’re not properly timed so there’s some “sparkling” on a C64C or C128. The expanded sprite logo and scaled up scroller from the first NWCUG demo make a return, except with the former cycling through different colour schemes and the latter sporting cool-looking shadow effects. Hitting space gets another ESCOS-style part which this time reproduces the demo Power Windows but in all four borders, allowing the user to move the picture up and down under joystick control.

Finally, slapping Restore pulls up another sprite sinus part to finish the show which this time updates sixteen sprites with eight being displayed on each frame. It might be flickery – I was surprised that the YouTube video comes out as well as it does – but the routine comes with several presets to choose from and the option to play with various settings once they’re in motion. It also features my second favourite tune from all of the NWCUG demos playing behind it, a wonderfully laid back piece that fits the sedate, almost hypnotic movement of those sprites very well.

Almost all of the music in these three demos are original and enjoyable, the graphics are good throughout in part because there’s a couple of “borrowed” Bob Stevenson works in there and the code is for the most part solid. I remember originally watching the second and third NWCUG demos as a teenager after a friend downloaded them – I didn’t see the first until some point in the 1990s if memory serves – and being completely blown away at the time. All three have a unique style throughout despite their being collections of parts and, for me at least, still hold together well now.

Releasing Level One (C64)

We’ve reached the end game for 2018’s Intro Creation Competition so there’s been an inrush of new releases over the last couple of days including one last contribution from yours truly with the ever patient Andy Vaisey on music. It went through a few names but Level One was the final choice simply because it looks somewhat like a game.

The scrolling area takes up the entire regular screen – 39 visible characters across by 25 down – and is being moved using a double buffered scroll routine similar to the ones employed by games which in turn leans on some Run-Length Encoded background data. It also uses the C64’s Extended Colour Mode so, although there are only 64 characters available in the font, it can have four possible background colours for each character so I don’t have to scroll the colour RAM.

Something a little trickier is happening in the black bands above and below the scrolling; these are ten pixels high and sat in the borders, but containing a seven character wide Cosine logo and nineteen characters of either static text or scrolling message. To get twenty six characters into that space the code has to abuse the ghostbyte, splitting it at five points on each scanline to produce the extra two characters (they’re at the far left and right of the screen on both lines) and mask off the raster bars for the areas between the sprites.

I suspect a few people will be asking themselves if a game with similar graphics would be possible and the answer is a sort-of-yes, although drawing decent backgrounds when restricted to just 64 characters is bloody tricky!

Watching Snata (C64)

Released in 2002, Snata was an entry into the Christmas Demo Competition and not in the slightest bit cynical or sarcastic. Well, okay it was because the “inspiration” was a SuperCPU-specific demo called Coca Cola Santa Claus – the original seems to be lost to the mists of time – which used the 65816 to brute force a full screen width FLI image out of the VIC-II… and then displayed one of the worst-looking wired pictures I’ve ever seen! So on a particularly dreary winter evening I was making a nuisance of myself on IRC and ended up in a little “competition” with Groepaz where we amused ourselves by taking said image and trying but failing to produce something similarly terrible by throwing it through whatever converters we had to hand.

A year or so before this evening of entertainment happened I’d noticed in passing that the tunes from Zeppelin’s Amiga game Santa’s Xmas Caper were all written in the same general, annoyingly jolly style so, pretty much on a whim that I was probably at a loss to explain even then, I spent an evening unceremoniously mangling them into a single piece with Goattracker. So now I had a piece of music and a fairly reasonable wired picture, so all that was needed for a Christmas competition entry was a little code to glue it together and that was actually donated by a previous release.

But once that had been congealed I had a moment of what we’ll have to call “inspiration”; since the picture had been based on a demo which required a hardware expansion to run it seemed sort of appropriate to add a similar but in this case optional overhead to mine and I already had just the thing lying around, a routine which leant on a RAM expansion to produce an effect similar to the FLI-based one in Charlatan – appropriate considering Coca Cola Santa Claus – but in the borders rather than on screen.

The routine uses the REU’s DMA to transfer colour data back and forth between the base 64K and expansion RAM, moving everything around at an impressively fast one byte per cycle. There are two shifts of the colour data during the screen to update it but the important part happens during the upper and lower borders where transfers are triggered with the destination set to $D020 and the DMA told not to update that address with each write; the result is that the border colour register is updated once per cycle with around 48 being visible but 63 writes actually taking place since there’s that many cycles per scanline.

Of course, the competition was just for fun and meant to be just standard C64 code so the colour bars were only there as a hidden bonus, but hey ho ho ho…