Stand in the middle of a straight road and its edges run together at the horizon. Tilt your view along one line of tarmac at a time and every line of the screen below the horizon matches one distance ahead of the car. That observation is the whole of the pseudo-3D road. The road has no geometry at all. The program decides, for each screen line, which slice of road it shows, how wide it should be and how far to shift it sideways or up and down. Sega’s Turbo had it in arcades by 1982, with hills, tunnels and night driving. Namco’s Pole Position made it a Grand Prix, and Sega’s Out Run (1986) made it the look every home computer tried to copy. The programmers who wrote those copies started with the road, because everything else in the game hung on it.
Fast facts
- Early arcade example: Sega’s Turbo, in American arcades by spring 1982, “the most graphically outstanding car race videogame ever created” (Electronic Games, June 1982).
- The chart-topper: Pole Position (Namco, built in America by Atari), “this year’s champion in the tire-squealing sweepstakes” in 1983.
- The high-water mark: Out Run, September 1986, on Sega’s sprite-scaling hardware with a dedicated road chip.
- The rule of the trade: “We always do the road first” — Pete Hickinson of Teque Software, 1989.
How it works
Draw a horizon line and treat every screen line below it as a slice of road at some distance ahead. Perspective says that apparent size falls in proportion to distance. The line just below the horizon is very far away and the bottom line is just in front of the bumper, so the program can work out once, in a table, the distance each line stands for and how wide the road should be drawn there. On a straight road the result is a wedge whose edges meet at the horizon.
Speed comes from colour, not from moving the picture. Real roads have stripes, kerbs and lane markings at regular intervals. The program picks each line’s colour from the distance that line represents plus how far the car has travelled, so a band of alternating colour slides down the screen, slowly near the horizon and fast near the bottom, exactly as markings on a real road would. Hickinson’s warning in 1989 was that pushing the road picture at the screen “really quickly” makes it look as though it is going the wrong way; the trick is objects that “appear to move more slowly the further away they are, even though the actual speed doesn’t change.”
Bends are a sideways shift. The track data says how sharply the road curves at each point. Working up the screen from the bumper, the program adds that curvature to a running step and adds the step to a running offset, then draws each line shifted by the offset. The road under the car stays put while the far end swings away in a smooth curve, and a curve that changes sign partway along becomes an S-bend. The player’s steering moves the whole road the other way.
Hills are the same idea turned vertical. A rise ahead pushes the far lines up above the flat horizon; a dip lowers them, and over a crest the road beyond simply drops out of sight, hidden behind the brow. That was the difference British reviewers noticed in Out Run: “Unlike Pole Position, Out Run’s road swoops up and down … you often shoot straight over the brow of a hill and mangle yourself under a truck” (Sinclair User, October 1987).
Cars and scenery are flat pictures drawn at a size taken from the same distance table and placed at the road’s offset for that distance, farthest first so that nearer objects cover farther ones.
With the tables prepared, none of this needs much arithmetic per line, which is why it worked on a Z80 or a 6502. What it cannot do is let the player leave the road or turn round: the world exists only as a strip unrolling ahead of the car.
Arcade origins
Racing games had looked down the road before. Electronic Games recalled in 1983 that Atari’s Night Driver, “Atari’s coin-op simulation of white line fever”, had “failed to dent the arcade on-ramp”. What changed things, the magazine said, was Turbo: “Only when Sega dared the laughter of the cynics by marketing Turbo did racing games get a serious second look.” The game had reached arcades in 1981, according to MAME and Sega Retro, and by May 1982 it was one of the most popular machines at the Circus Circus arcade in Las Vegas. Its June 1982 review read like a tour: a tree-lined highway with mountains in the distance, a city, night with street lights, then hills where other cars “rise and fall from view as they climb and descend the mountainous geography”, then tunnels lit only by lane markers. Sega’s hardware scaled its sprites by slowing the clock that read them out (see sprite scaling).
Pole Position, “a first-person driving game developed by Namco in Japan and distributed to this country’s arcades by Atari”, was the champion of 1983 for a different reason. It brought “the Fuji Speedway and Grand Prix conditions” to the arcade, with a qualifying lap to finish “in 73 game seconds or less” and billboards along the track. Electronic Games called it “an eye-popping spectacle, but the focus here is on your car’s position regarding the other participants.”
Sega’s answer was more scaling hardware. Yu Suzuki’s Hang-On (July 1985) put two 68000 processors, a sprite-scaling chip and a separate road chip on one board; Space Harrier (December 1985) used the same road chip for its chequered ground. Out Run (September 1986) followed. Suzuki later called it “the first game to use the Super Scaler technology”, though other accounts start the line with Hang-On. ACE singled out its “large (and frighteningly solid) pieces of roadside scenery” that “hurtle past very convincingly”, and the end-over-end crash when you hit one.
By 1989 polygons had arrived in arcade racers. Atari Games’ Hard Drivin’ and Namco’s Winning Run, both shown at the same London trade show early that year, built their tracks from solid shapes, and Hard Drivin’ let the player leave the road, jump a drawbridge and drive round a loop.
The road first
When The One visited Teque Software in 1989, Pete Hickinson and Bill Caunt were converting Taito’s Chase H.Q. to the Atari ST and Amiga for Ocean, having just done Continental Circus. Asked where they started, Hickinson said: “On the road. We always do the road first — that’s the central routine that the entire game is based on, so it’s vital to get that working first.”
He called a moving, winding road “really just a mathematical exercise”, but the code did not carry from one game to the next. “The principle is pretty much the same in both games, but we’ve had to produce the road calculator and most of the maths from scratch. Chase has a more complex road system than Circus — it changes in width, passes through tunnels and even breaks into two separate roads.” A change of width was done with “small ‘snakes’ in the side of the road that move it inwards or outwards. And when two appear together (one on each side) the road is thinned or widened.”
The same game shows what the road routine meant on an 8-bit machine. Ocean’s own Spectrum Chase H.Q., which scored 95% in CRASH, began with John O’Brien rewriting the road engine from WEC Le Mans to run more than twice as fast; the Chase H.Q. entry tells that story.
On home machines
Home computers had no scaling hardware, so everything was done in software, and the sacrifices showed. US Gold’s 8-bit Out Run conversions arrived for Christmas 1987. ACE found the C64 version gave “a good impression of speed”, but “all vehicle patterns are fixed and learnable”, and the Out Run entry follows how each version traded one feature for another.
On the Super NES the road competed with the console’s own Mode 7 rotating background. Gremlin’s Top Gear (1992) used a software road anyway. Ritchie Brannan, “responsible for the road and sprite routines”, told ACE that its “road moves faster and the corners and hills are more extreme to try to make the game faster and more cartoon like”, and that “‘Give me a faster processor and I’ll do it’ is a poor and over-used excuse”. His next job was “a road routine with more than twice the depth of Top Gear and a much smoother feel”.
Sources
- Electronic Games vol. 1 no. 3, May 1982: Turbo among the most popular games at Circus Circus, Las Vegas.
- Electronic Games vol. 1 no. 4, June 1982, p. 56: Turbo review.
- Electronic Games vol. 1 no. 16, June 1983, pp. 93–95: Pole Position review.
- Electronic Games vol. 2 no. 7, September 1983, pp. 65–66: racing games feature (Night Driver, Turbo, Pole Position).
- MAME source code,
src/mame/sega/turbo.cpp(Turbo, Sega, 1981), and Sega Retro, “VCO Object” (web, secondary): Turbo’s release in 1981 and its scaling hardware. https://github.com/mamedev/mame and https://segaretro.org/VCO_Object - Sinclair User issue 67, October 1987: coin-op feature on Out Run.
- ACE issue 5, February 1988, pp. 38–39: Out Run review.
- The One issue 14, November 1989: Chase H.Q. work in progress at Teque Software.
- ACE issue 54, March 1992: Top Gear preview.
- Edge issue 9, June 1994, pp. 45–50, “Yu Suzuki: Sega’s driving force”.
- ACE issue 19, April 1989, pp. 22–23, and The Games Machine issue 16, March 1989: Hard Drivin’ and Namco’s Winning Run at the Amusement Trades Exhibition, Olympia.
- For the Sega boards’ road and sprite chips, see the citations in the Hang-On, Space Harrier and sprite scaling entries; for the Spectrum Chase H.Q., the Chase H.Q. entry.