Amiga coders still talk about “Kefrens bars”: a wall of vertical bars that twist and weave down the screen, each one seeming to stand in front of the last. The name comes from a Danish group that spent the late 1980s turning out numbered megademos, went quiet, and then in April 1993 won the Amiga demo competition at The Gathering in Norway with Desert Dream. Amiga Format introduced them that summer as “a long-standing demo group who don’t often release work – but when they do… you can bet that it’s impressive.”
Fast facts
- From: Denmark.
- Active: from 1987 as The Starlight Project, as Kefrens from 1988; the last productions listed for the group date from December 1993.
- Platforms: Amiga, with a couple of Commodore 64 demos in 1989.
- Best known for: Desert Dream, first at The Gathering 1993; the megademo series; the effect named after them.
- Members included: Razmo, Metallion and Mellica (founders), Promax, Laxity, Vention and R.W.O. The musician Jesper Kyd is credited on Kefrens productions from 1988.
Megademos
According to the scene database Demozoo, Kefrens began in 1987 as The Starlight Project, founded by Razmo, Metallion and Mellica. A demo from June 1988 announced the change: “TSP is now called Kefrens”. The group’s early output was the usual mix for an Amiga group of the time: intros, cracktros, compilation packs and a run of numbered megademos, each a disk of separate demo parts by different members.
Those disks travelled through public-domain libraries. In July 1989 ST Amiga Format’s Demos Corner waded through “the usual collection of mega-copper-blitter-nutter demos” and chose a best disk of the month. On it, “Probably the most visually impressive demo was the ‘Kefrens Psychoball’ demo which employs sampled effects, large multi-colour blitter objects and very smooth scrolling.” Demozoo credits Psychoball’s code and graphics to Promax, with music by Nightlight.
Megademo VIII followed in February 1990, released at a party Kefrens held with the group Dexion in Nykøbing Falster, Denmark. Its credits, as Demozoo lists them, show how many hands a megademo took: code by Gizwiz, ICronite, Mellica, Metallion and Promax, graphics by Box, Milkshake and The Whiz Kid, and music by Jesper Kyd and Nightlight among others. Promax also wrote tools; Demozoo credits him and Detron with the code of the assembler Asm-One under the Kefrens name.
Quiet years and a comeback
After 1990 the output slowed. One 1991 intro was titled Death of Kefrens – Where Are They Now?. A smaller team of coders Laxity and Vention, graphic artist R.W.O. and musician S.L.L. made Guardian Dragon in 1991, Egregious, which they entered at The Party in Denmark that December, and Guardian Dragon II in 1992.
In 1993 the group was, in the words of the Italian Amiga Magazine, an old group “revived for the occasion”. Desert Dream, coded and scored by Laxity with graphics by R.W.O. and others, won the Amiga demo competition at The Gathering in Lillestrøm in April. Seven weeks later, at The Computer Crossroads in Gothenburg, Sweden, Kefrens’ D.A.N.E. came fifth in the Amiga demo competition and R.W.O. came second in the graphics competition. British public-domain libraries sold both demos. In September 1993 one of them, Visage Computers, told Amiga Format that Desert Dream and D.A.N.E. were its first and third most popular demos of the month.
A few more productions followed that year, among them Ankh in Popland for the new AGA Amigas. The public databases list nothing from the group after December 1993.
Kefrens bars
Kefrens bars are a wall of vertical bars: each bar is a narrow coloured band with its own shading, and a column of them snakes down the screen in a curve, every bar partly hiding the ones above it. The group’s name stuck to the effect, and demo coders use it for any version on any machine. Public sources do not establish which demo showed it first.
The usual way to make it on an Amiga needs almost no screen memory. Instead of a full bitmap, the program keeps one line of pixels and shows it on every line of the display. It then draws a bar into that line, at a new horizontal position, as each line of the screen is drawn. Nothing is ever erased during the frame, so each line of the picture shows every bar drawn so far, with the newest one on top. Down the screen the bars pile up into the familiar twisting wall.
The hardware that makes the repeated line possible is the bitplane modulo. Commodore’s Hardware Reference Manual explains that when the display reaches the end of a line, “the modulo is added to the bitplane pointers”, so that the next line’s data is fetched from the right place. With a normal screen the modulo is 0, and the pointers run on through memory. Set it to minus the length of one line, in bytes, and the pointers go back to the start of the same line every time. Keeping a change in step with every line of the display is the kind of job the Amiga’s copper exists for: it waits for the beam to reach a line and writes the custom chips’ registers there, while the processor or the blitter does the drawing.
Sources
- ST Amiga Format issue 13, July 1989, p. 38: Demos Corner, Amiga section, on Psychoball.
- Amiga Format issue 48, July 1993, p. 159: PD Demo Zone, Andy Nuttall, review of Desert Dreams, with the caption on Kefrens.
- Amiga Format issue 50, September 1993, p. 158: “Top Ten Demos of the Month”, from Visage Computers (Desert Dream first, Dane third).
- Amiga Magazine (Italy) issue 94, November 1997, pp. 22–23: history of the Amiga demo scene; Kefrens among the groups active from 1986 to 1988, and “revived for the occasion” in 1993.
- The Gathering 1993, competition results (web, secondary copy of the organisers’ file): https://files.scene.org/get/parties/1993/thegathering93/results.txt
- The Party 1991, results (web, secondary copy of the organisers’ file): Egregious among the entries. https://files.scene.org/get/parties/1991/theparty91/results.txt
- The Computer Crossroads 1993, results compiled from disk magazines and party reports (web, secondary): Amiga demo and graphics competitions, 29 to 31 May 1993. https://files.scene.org/get/parties/1993/computer_crossroad93/results.txt
- Demozoo, group entry for Kefrens and its production entries (web, secondary): founding and renaming, members, release dates and credits for Psychoball, Megademo VIII, Asm-One, Guardian Dragon, Egregious, Guardian Dragon II, Desert Dream and Ankh in Popland. https://demozoo.org/groups/658/
- Amiga Hardware Reference Manual, 3rd edition (Commodore-Amiga, Addison-Wesley, 1991), chapter 3, “Playfield Hardware”: the bitplane modulo and how it is added to the pointers at the end of each line (pp. 60–61), and negative modulo adjustments for scrolling.
- Wikipedia, “Raster bar”, section “Vertical raster bars” (web, secondary): the same line of video memory output on every scan line, with a new bar added each line.