The LAGOON OF TRANQUILITY saw its debut at the 2005 Contact Conference at NASA Ames in Mountain View, CA.  Participants were able to feed virtual sea-creatures via an infrared-sensing tabletop. Creatures respond to the release of food particles triggered by motion detected over the surface of the tabletop.

Participants enjoying the "Lagoon of Tranquility"

Complete setup at the Contact art show

Typical tabletop projection image

The tabletop "Lagoon of Tranquility" exhibit was run by two PCs, and a monitor near the exhibit displayed what the infrared camera was seeing.  The monitor displayed little sparkles where motion was being identified in the image.  It turned out that this display was nearly as fascinating to the participants as the interactive display on the table itself.

"Behind the scenes" monitor of infrared activity

The skirt of the table was folded back at one corner so visitors could see what was going on inside.

Visitors were allowed a peek at the innards

Construction Details:

A - Power connections
B - Projector
C - Infrared illuminators
D - Stereo speakers
E - First surface mirror
F - Cold mirror
G - Subwoofer
H - Reflection-blocking baffle
I - Infrared video camera
J - CD Player

Ambient sound for the exhibit was produced by a looped CD.

Future Directions/Issues:

The size of the projection on the tabletop didn't quite take full advantage of the tabletop, due to the relatively short distance of projection.  In fact, the tabletop had to be adjusted several inches higher than the original target in order to produce a sufficient image size.  Some mirror bounce underneath the table was implemented in an attempt to correct for this, but was limited by the restrictive size of the cold mirror. One alternative might be to bounce off the cold mirror first, then off a larger first-surface mirror.  Positioning the mirrors was troublesome as well (yes, that is an erector set construction that is supporting them).

The plexiglas top is quite shiny, and does present some reflection issues even if there are no lights directly overhead.   Some positions around the table were affected by overhead lighting that was several feet outside the exhibit area.  An alternative could be to tilt the table more like an easel, but the horizontal top as used here even with the reflection issues still provides for more simultaneous users than an easel approach would allow.

Using the cold mirror as a "beam splitter" was very effective in removing trapezoid distortion in the camera image, only simple scaling was necessary to calibrate the camera coordinates to the display coordinates. The cold mirror was an antique glass mirror made by Kodak for enlarger applications (used because it was on hand), and did subtract a notable amount of visible red out of the projection, a more modern substrate based mirror may be an improvement.

Sensitivity of the table was excellent, it was able to pick up any motions over the projection that were anywhere within about 6 inches above the tabletop.