How it worked
A raster display — used by the vast majority of games then and now — works by scanning an electron beam across the screen in horizontal lines, top to bottom, 60 times per second. Each point on the grid is set to a specific colour or intensity. The resolution is fixed; the image is composed of a grid of discrete points. Drawing a diagonal line on a raster display requires lighting up a staircase of pixels — at low resolutions, the diagonal appears jagged.
A vector display — used by Asteroids, Tempest, Battlezone, Space Wars, Gravitar, Major Havoc, and Star Wars — works entirely differently. The electron beam is directed explicitly along mathematical paths. The display controller sends the beam from point A to point B along a straight line — a vector — then from B to C, then C to D. The beam traces the outline of shapes rather than scanning a fixed grid. The result is geometrically perfect lines at any angle, with no jaggednes and no pixel grid. A circle on a vector display is a smooth curve; on a raster display of equivalent resolution it is an obvious polygon.
The vector display's strength was the quality of its line rendering. Its weakness was that it could only draw lines — filled areas, gradients, and the kind of complex sprite animation that raster displays handled well were impossible or extremely difficult. Vector games were necessarily geometric: wireframe spacecraft, outlined asteroids, skeletal buildings. The aesthetic was not a stylistic choice. It was the direct consequence of the display technology's capabilities.
Asteroids and the ideal form
Asteroids (1979) was the game for which vector graphics were ideally suited. The game required irregular polygon shapes — asteroids of varying sizes — that rotated at arbitrary angles and fragmented when shot. On a raster display of 1979, rotating irregular polygon shapes would produce severe aliasing artifacts and require significant processor time to redraw. On a vector display, rotation was mathematically trivial — the same points were simply rotated around their centroid before being drawn — and the result was perfectly smooth regardless of angle.
The fragmenting asteroids — a large asteroid breaking into two medium ones, which broke into small ones — was similarly natural for vector hardware. The game engine maintained a list of polygons and their positions; breaking an asteroid meant replacing one polygon record with two smaller ones at nearby positions. The display hardware drew whatever polygons the game engine described. The mechanic that made Asteroids distinctive was, at a technical level, a consequence of working with a display that thought in terms of lists of lines rather than grids of pixels.
Tempest and colour vectors
Early vector displays were monochrome — a single colour of phosphor, typically white or green, excited by the electron beam. Colour vector displays, which appeared commercially around 1980, achieved colour through a different approach: multiple electron guns targeting different phosphor layers, or coloured filters placed over sections of the screen. The results were impressive but technically complex.
Atari's Tempest (1981) used a colour vector display with a colour encoder that could set the beam's intensity and colour independently for each drawn segment. The game's distinctive visual palette — bright shapes against a pure black background, with different enemy types rendered in different colours — was possible because the hardware could set colour segment by segment. The visual effect was striking in a way that raster games of the period couldn't match: pure, saturated colours against absolute black, without the background noise or colour bleeding of raster phosphor displays.
Why it ended
Vector displays had two fundamental commercial problems: they were expensive and they could not display the kind of content that players increasingly expected from arcade games by the mid-1980s. A vector display monitor cost significantly more to manufacture than a raster CRT of equivalent size. The specialist vector display hardware required in the arcade cabinet added further cost. As the competitive pressure on arcade game prices increased, the premium that vector hardware commanded became harder to justify commercially.
The content problem was structural. By 1982–1983, the most successful arcade games — Pac-Man, Donkey Kong, Galaga, Frogger — used coloured sprites on raster displays. Players expected characters with visual personality, backgrounds with texture, and animation that conveyed character. Vector hardware could not produce any of these things. The wireframe aesthetic that had been technically distinguished in 1979 read as primitive by 1984, even though the geometry was still cleaner than anything raster hardware produced.
The last significant commercial vector arcade games were released in 1983–1984. Star Wars (Atari, 1983) used colour vectors to recreate the Death Star trench run with a fidelity that raster technology couldn't have matched. It was also, commercially, the end of the form. After Star Wars, vector hardware appeared only in specialised contexts. The aesthetic it produced — clean geometric shapes, pure black backgrounds, mathematically perfect curves — has been revived repeatedly as a retro reference, most visibly in the indie game aesthetic of the 2000s and 2010s. The technology itself is gone.