Vector Graphics | Code Like It's 198x

A television draws the same picture every time: it sweeps its electron beam across the screen in rows, top to bottom, and lights dots along the way. A vector monitor lets the program steer the beam instead. It moves the beam from one point to another with the beam switched on, and leaves a bright, thin line behind; it moves it with the beam off, and nothing shows. There are no pixels, so a line comes out sharp at any angle and a shape can be rotated or shrunk just by changing the numbers. For about seven years, from Cinematronics’ Space Wars to Atari’s Star Wars, this was how some of the arcade’s most famous games looked, and in 1982 the Vectrex brought one into the home.

The words had a second life. On home computers, which only had raster screens, “vector graphics” came to mean 3D shapes stored as lists of corner points and drawn as lines between them: Elite’s ships, Starglider’s walkers. The results looked alike, but the machinery was different, and the two senses are worth keeping apart.

Fast facts

In the arcades: a display that draws lines by steering the beam. Cinematronics’ Space Wars (1977) was the first coin-op to use one.
Atari’s name: QuadraScan, “essentially the same system, but the name is trademarked for use exclusively by Atari” (Electronic Games, 1982).
Colour: Sega’s Space Fury and Atari’s Tempest, both 1981. Before then vector games were black and white, often under a coloured plastic overlay.
At home: the Vectrex (GCE, 1982), with its own 9-inch vector screen. Electronic Games called it “the only vector-based home videogaming system”.
On home computers: “vector graphics” meant wireframe 3D calculated from coordinates and drawn into screen memory, as in Elite (1984). Filled shapes built the same way were called “solid vector graphics”.

Drawing with the beam

The program in a vector game does not fill in a picture in memory. It writes a list of instructions: move here, draw a line to there at this brightness. Hardware reads the list and drives the monitor’s deflection circuits directly. In Asteroids the 6502 builds the list in 2K of memory and a separate circuit, the vector generator, draws it while the processor fills a second list for the next frame. The Vectrex does the job with a single digital-to-analogue converter and a pair of integrators, so the length of each line depends on how long the processor holds a switch open.

Electronic Games explained the difference to readers in 1981 as that “between a connect-the-dots puzzle and the smooth lines of an etch-a-sketch”. It pointed out a second advantage: QuadraScan “makes it possible for objects to drift onto the screen from any direction and at variable speeds”. Nothing is locked to a grid of pixels or characters, and a 3D wireframe costs only its edges.

The limits come from the same design. Nothing can be filled in: it was, the magazine wrote in 1984, “just about impossible to produce real-looking images due to the lack of shading, and large areas are often left empty of detail”. Every line has to be redrawn on every pass, so a busy screen takes longer to draw; the Vectrex’s manual warns owners that “it may appear that the images pulse”. A beam that stops moving burns a spot in the phosphor, so both Asteroids and the Vectrex have circuits that shut the display down when that happens. And the monitor was specialised hardware, not a television. “Vector’s biggest drawback is its considerable cost,” said Electronic Games, “at least in arcade machines.”

From Spacewar! to Space Wars

The idea came from a computer laboratory. Spacewar!, written by students at MIT in 1962, ran on a DEC PDP-1 minicomputer with a Type 30 Precision CRT Display. That screen did not draw lines: DEC’s handbook describes “random point plotting” on a 1,024 × 1,024 grid, at 20,000 points a second, with one instruction to light one dot anywhere on the tube. Line drawing already existed on computer displays; the same handbook notes that some variations of the Type 30 “include hardware for line and curve generation”.

Getting a space battle into an arcade took cheaper hardware. One early attempt, Pitts and Tuck’s Galaxy Game, put a DEC PDP-11 minicomputer and its vector display terminals into cabinets: in Retro Gamer’s words, “a mini-computer with a coin slot”. Larry Rosenthal, an MIT graduate, took a different route. According to Retro Gamer, he built a board of TTL logic chips that copied the instruction set of the smaller DEC PDP-8, so that it could run the PDP-8 version of Spacewar!, which he licensed from MIT, on a vector monitor. Midway turned it down, Video Games reported in 1982. Cinematronics, a small Californian company close to going out of business, took it on a 50/50 split and released it as Space Wars in 1977. Wireframe called it the biggest arcade game of that year and the next, and Retro Gamer put the number built at about 30,000.

Space Wars gave two players thrust, fire and hyperspace buttons, and Electronic Games noted that earlier games “had fewer controls (usually one or two)”. The magazine went further, writing in 1984 that Rosenthal “is widely credited with having invented vector graphics”. What he had done was bring them to the arcade. He then left to start a company of his own, Vectorbeam, and Cinematronics carried on with vector games including Starhawk, Tailgunner and Star Castle.

QuadraScan and the arcade boom

Atari’s own vector display grew out of a prototype from its research group, and its first vector game, Lunar Lander, came out in 1979. Electronic Games remembered it as “Atari’s most talked-about game, at least partly because of its novel vector graphics”. Then, “when fans clamored for more”, came Ed Logg’s Asteroids at the end of 1979, “the most talked-about vector-graphics game of all time”. Asked in 1982 how QuadraScan differed from Cinematronics’ system, the magazine answered that there was “no real difference”.

The display suited first-person 3D, because a wireframe landscape is just more lines. Battlezone put the player in a tank and Red Baron in a fighter plane; QuadraScan, wrote Electronic Games, “creates images as three-dimensional, crystaline objects, detailed schematic line drawings of reality”.

Colour arrived in 1981. According to Electronic Games, until Sega’s Space Fury, “game players were either playing vector games in black & white, or vector games with a colored plastic overlay on the screen”. Atari’s first colour vector game was Dave Theurer’s Tempest, released the same year; Electronic Games called it in 1982 “not only the most visually striking coin-op around, but one of the most challenging as well”. Sega itself stayed mostly with raster screens, and the magazine counted its raster games outnumbering its vector ones by “five to one”.

By September 1984 Atari’s Star Wars was “one of the hotter games gobbling tokens right now”, but the magazine was unsure what came next: laserdisc games were arriving, and “the future of vector is unpredictable”. Its list of the best vector games named Atari’s Asteroids, Battlezone, Star Wars and Tempest, Bally/Midway’s Omega Race, Cinematronics’ Star Hawk and Tailgunner, Sega’s Space Fury and Star Trek, and five Vectrex cartridges.

The Vectrex

General Consumer Electronics launched the Vectrex in the autumn of 1982 at around $200, with a 9-inch black-and-white vector tube built in. Electronic Games described “delicately etched line drawings in brilliant black and white” with “a very pronounced three-dimensional perspective that is especially effective in the outer space games”. Plastic overlays added colour, as they had in the arcades, and the catalogue included home versions of Cinematronics’ Space Wars, Star Hawk and Star Castle. By 1984 the Vectrex had gained a light pen and a 3-D imager with colour goggles, which Electronic Games took as a sign that “technology has caught up to the Vectrex”. It was also the year Milton Bradley stopped making it. The Vectrex entry tells that story.

Vector graphics on home computers

A home computer drew on a raster screen, but it could still use the method behind the vector games. Each object was stored as a list of corner points in 3D space. The program rotated and moved those points, worked out where each would appear on screen, and drew straight lines between them into screen memory, one pixel at a time. The Games Machine explained it in 1989: objects “are defined by vectors … which pinpoint the major points of an object”, and “lines are then drawn between these points to construct a wireframe graphic as in Elite and Battlezone-type games”.

The British magazines called this vector graphics. Reviewing Firebird’s Spectrum version of Elite in January 1986, Your Computer wrote that “what, of course, sets this game apart is the use of vector graphics”. The cost was processor time: every point had to be multiplied through for every frame, and the screen had to be cleared and redrawn. ZZAP!64 reported in 1985 that the Commodore 64 Elite ran “quite a bit more slowly” than the BBC Micro original, partly because the BBC’s processor ran at a higher speed and partly because “vector graphics are harder to program on the 64”. In play, the reviewers added, it did not seem slow at all.

Wireframes had their own problem: you could see through them. Starglider (1986) stood out because it removed hidden lines, so a ship’s far edges no longer showed through its near side. The next step was to fill each face with colour. The Games Machine noted that “strictly speaking, there are no such things as solid vector graphics”: they were filled polygons, produced by routines like the wireframe ones, harder to program but more realistic. The magazines never settled on one name for them. ACE greeted Starglider 2 in 1988 with “gone are the vector graphics of the original game”, while ST Amiga Format praised the same game for putting so many “vector graphics” on screen at once.

Flat polygons without any 3D are something else again. Another World (1991) draws every image as flat, filled 2D shapes, not wireframes and not 3D models. The One explained in 1991 that its introduction, several minutes long, fitted in under 100K of polygon data and program, where “traditional bitmapped artwork would take up an entire disk”. It shares the idea of describing a picture by its corner points, but it is a polygon game, and none of these home computer games had anything to do with a vector monitor.

Sources

Electronic Games vol. 1 no. 1, Winter 1981 (December 1981), p. 32: Asteroids and Quadrascan (the connect-the-dots comparison; objects entering from any direction).
Electronic Games vol. 1 no. 2, March 1982, p. 53: reader’s question on Vectorbeam and Quadrascan (“no real difference”; the Atari trademark). p. 70: Red Baron (“crystaline objects”).
Electronic Games vol. 1 no. 3, May 1982, p. 60: Coin-Op Corner, Tempest as “Atari’s first vector graphics system videogame in color”.
Electronic Games, November 1982, p. 26: Vectrex review (the etched line drawings and 3D perspective).
Electronic Games vol. 1 no. 14, April 1983, p. 84: Space Wars “premiered vector graphics in videogames”.
Brian Scott, “Vector Graphics”, Electronic Games vol. 2 no. 14, September 1984, pp. 68–70: advantages and drawbacks; Space Wars, its controls and Rosenthal; Starhawk and Tailgunner; Space Fury and Sega’s five-to-one; Lunar Lander and Asteroids; the Vectrex; Star Wars; the list of the best vector games.
Andrea Stone, “The House That Pac Built”, Video Games vol. 1 no. 3, December 1982, p. 53: Rosenthal, Midway and Cinematronics.
Marty Goldberg, “The Making of Star Castle”, Retro Gamer issue 112, 2013, pp. 84–87: Cinematronics’ finances; Galaxy Game; Rosenthal’s TTL copy of the PDP-8 and the MIT licence; the 50/50 split; Space Wars in 1977 and about 30,000 built; Vectorbeam; Starhawk and Star Castle.
Wireframe issue 35, March 2020, p. 46: Spacewar! on the PDP-1.
Wireframe issue 64, June 2022, p. 27: Space Wars in 1977, the biggest arcade game of that year and the next.
“The Making of Tempest”, Retro Gamer: The Atari Book, 2012, p. 150: Tempest officially released in 1981.
Digital Equipment Corporation, PDP-1 Handbook (F15D, 1963), pp. 33–34: the Type 30 Precision CRT Display (random point plotting, 1,024 × 1,024 locations, 20,000 points a second, the dpy instruction, variations with line and curve generation).
General Consumer Electronics, Vectrex service manual and owner’s instructions (1982): the pulsing warning and spot-burn protection, as set out in the Vectrex entry.
Atari, Asteroids program listing (1979; published by the historicalsource archive on GitHub, 2021): vector RAM, the vector generator and the double-buffered display lists, as set out in the Asteroids entry.
Lee Paddon, Elite review (Spectrum), Your Computer, January 1986, p. 41.
ZZAP!64 issue 1, May 1985, p. 17: Elite on the Commodore 64 (speed, and vector graphics on the 64).
Robin Candy, “Solid as a Rock”, The Games Machine issue 20, July 1989, pp. 16–18: how vector graphics are built, wireframes and “solid vector graphics”.
ACE issue 13, October 1988, p. 75: Starglider 2 review. ST Amiga Format issue 4, October 1988, p. 53: Starglider 2 review.
The One issue 37, October 1991, p. 10: Another World preview (the polygon animation system; 70K of animation data and 15K of program).