|Q:||Which 1980 arcade game first demonstrated the animation technique now known as "flocking?"|
|A:||"Rip-Off" was the flocking game. Also the first cooperative-play arcade game, it featured smart enemies that sought out target objects and could change goals while avoiding collisions with each other.|
|--- Trivia slide, SIGGRAPH 2001 Electronic Pre-show|
This is not intended to be a history of the 1980 video arcade game "Rip-Off," which I designed and programmed. However, a little background will help explain why and how its computer-controlled opponents had an unusual amount of intelligence for the time..
By 1980 video arcade games like Pac-Man were beginning to show glimmers of today's "game AI," but their low-resolution displays limited movement of player and game icons to a very predictable left, right, up and down. Games with vector displays like Larry Rosenthal's Vectorbeam system displayed their linear graphics at high resolution, which allowed rotation and movement without image degradation. Unfortunately, low screen refresh rates limited vector games to virtually blank, black screens populated with small clumps of glowing lines. The only way for manufacturers of vector-based systems to compete was to create games that featured superior game play that only these displays could provide. One simple example to consider -- would Atari's "Asteroids" been possible, let alone popular, on an extremely low-resolution raster display? Not too likely.
The line-drawing limitations of video game vector displays meant that game tokens, icons and characters had to be small and few in number. Even using very short and very few lines, "Rip-Off" displayed only two player figures, three "enemy" figures and eight small triangles representing the objects to be "ripped off." Game scores were only displayed between waves of attackers.
The game play was this -- one or two players working together protected the eight "canisters" placed initially in the center of the screen. Up to three enemy "tanks" would enter from the edges of the screen and attempt to attach a canister to themselves, which they would then attempt to drag off the screen. If a player's tank shot and destroyed an escaping enemy, the canister would be left where it was until picked up by another enemy. The game ended when all eight objects had been removed from the screen. No instructions were given to the enemy tanks to avoid player tanks. On contact with any other vehicle, player or computer controlled, the player vehicles exploded and had to "wait offstage" for a second or two.
There were no "lives" as in other games. "Rip-Off" was Players VS Entropy.
Prior to "Rip-Off," Vectorbeam programmer Dan Sunday created the popular game "Tailgunner." In it, he introduced a tiny amount of "game AI" to save on memory. Rather than store the paths of enemy ships in detail, he chose to store only key points along those paths. Once activated, his space ships oriented themselves towards their target points as they traveled forward along their own main axis. This resulted in graceful, curved paths that could not be easily anticipated by the player. Those paths were, of course, spline curves..
Armed with this "orient and move" behavior, I was able to give my enemy tanks enough intelligence to complete their tasks. This is what I programmed them to do:
So far, no significant departure from the seeking behavior used by Dan Sunday in "Tailgunner." But these enemies had more rules: