MIDSAC Pool Simulator

MIDSAC Pool Simulator
To play the MIDSAC Pool Simulator (MIPS), click on the "Cue direction" dial in the upper left corner and move the mouse left/right to set the angle of the pool cue. Click again when you're happy with the angle. Then click on the "Shoot" button (or the Ctrl key) to take a shot in the direction the cue is pointing. Try to knock the balls into the holes around the edge of the table without having the cue ball fall in a hole.

You can move the cue around the screen using the arrow keys or by clicking on the "Cue position" control. However, just like the original MIDSAC Pool, the trajectory of the ball does not depend on the position of the cue.

To reset the game, click on the "Re-rack" button. To just recover a scratched use the "Recover cue ball" button.

Note that the game will run more slowly the more balls are moving -- this is by design, intended to match descriptions of the original game. The frame rate varies from ~8 to 40 frames per second and depends primarily on how many balls are in motion.


The MIDSAC computer was developed at the University of Michigan in 1951-1953 and was capable of executing up to 25,000 calculations per second. It was the first of its kind in the midwestern USA and the sixth digital computer at a research university. There were two separate computers at the university, the MIDAC (Michigan Digital Automatic Computer) and the MIDSAC (Michigan Digitial Special Automatic Computer), and the pool game ran on the latter.

MIDSAC Pool is one of a handful of video games that is sometimes considered the first, depending on how you define a video game. Created in 1954, it post-dates the two other contenders I've simulated, the Whirlwind Bouncing Ball and the Cathode-ray tube amusement device, but offers a more complete experience than either of those games.

Most of the information I used to write this simulator was obtained from photos of the original game being played and transcribed testimony from a 1977 court case. The latter source includes a description of the pool game by its primary author, William George Brown.

For more information about the MIDSAC computer and MIDSAC pool, see this Norbert Landsteiner article.

The MIPS components

I believe that MIPS captures the key elements of MIDSAC Pool, but with only a written testimony and some photos to work from, some aspects of the simulation did require guesswork.

Ball motion

The motion of balls on a pool table can be derived from Newtonian physics that we've known about for centuries, so it's unlikely that the ball motions in MIPS differ substantially from the original game. However, there would have been minor differences, depending on the exact values of parameters used in the model (which are unknown) and whether any approximations were used in the calculations in order to make it run at a reasonable speed.

Parameters that could have been set differently include the initial speed of the cue ball, the coefficient of friction that slows the balls as they move along the table, and the coefficient of restitution that determines how much speed is lost when the ball bounces off the table boundaries. We do know that coefficients of friction and restitution were included in the model because they were mentioned in the court testimony, but the exact values are not specified.

The most complex part of the physical model is the ball collisions. In MIPS, I have treated all ball-on-ball collisions as elastic (that is, they conserve energy). It's not stated explicitly in the court testimony whether they used this assumption, but real billiard balls collide near-elastically and for the purposes of their demonstration, elastic collisions would have been good enough to make the motions look realistic.

The display

The MIPS display includes representations of the balls, the cue, and the table. The cue and the balls were rendered in real time by the cathode rays, and so would have shined brightly in the original MIDSAC Pool game. The table, on the other hand, was actually drawn on the screen with a grease pencil, so I show it in black in MIPS.

Note that I was going from black-and-white photos, so it's possible that the original game was colored. It's unlikely that it had the capability to display different objects with different colors, but the whole game may well have had, for example, a green or blue tint.

Persistence effects were substantial in these early vector displays, so MIPS overlays images of the last 300 positions of every ball, as well as the cue. The brightness of each image is set using a model I developed for the CRADS, with parameters set to approximate the trails seen in photos of the game.
One thing that puzzled me in the photos was that I couldn't see any way of distinguishing the cue ball from the other balls. It seems unlikely that the player was expected to keep track of the cue ball during a break, so I guessed that it was displayed at a different brightness. The balls are all saturated in the images I have, so if they had different brightnesses, it would be hard to tell.

The control panel

In MIPS, I only include controls that are directly related to the game. This includes a dial to set the angle of the cue, an analog joystick to set the position of the cue, a button to shoot the ball, a button to reset ("rack") the game, and a button to recover the cue ball after in case it falls in a hole.

There are other controls visible in the photos of MIDSAC Pool, but I don't know what their function was. It's likely that there were general purpose controls for calibrating the oscilloscope (e.g., aligning the beam in X/Y, setting overall brightness), but for the purposes of the MIPS simulator, I assume the display has already been calibrated.

Subsequent games

Pool simulations would make at least two other appearances in the early history of video games, both in the mid-60s and both mentioned in the Magnavox law suits. One was demonstrated in 1966 by Information Displays, Inc. and allowed players to move the cue around with a light pen, while another was demonstrated by RCA in 1967 at a research center in Princeton. For more information on games mentioned in the Magnavox law suits, see this article by the Golden Age Arcade Historian. It wouldn't be until 1976 that pool would appear in a commercial video game, with this coin-op by US Billiards.


  1. This is great - your attention to detail is fantastic - the verisimilitude is superb . Well done . I'm no coder but it looks like it was all done in vanilla JavaScript/HTML5 . It's so cool that we have people documenting computer history like this . On the philosophical side - I don't think it could be claimed that this constitutes an actual game but that's maybe for another time . Cheers.

  2. Yeah, how was this game created? This game is cool and retro!


Post a Comment