Multitoe, the floor you could type on with your feet

What it was

Multitoe came from the Human Computer Interaction Lab of Patrick Baudisch at the Hasso Plattner Institute in Potsdam, Germany. A team of nine wanted to carry the multi-touch table past its natural limit. A table you can touch directly cannot be deeper than your arm is long. A floor can be as large as the room.

The prototype was a pane of glass set flush with the floor, with back projection and a camera underneath. It used frustrated total internal reflection: light is fed into the glass and escapes only where something presses on it, so the camera sees the parts of a sole that touch as bright spots. From that image the software told users apart by their shoe profiles, ignored people who were only walking, and let one user draw, play a game or type.

PCWorld reported the test numbers when the floor was previewed at the CHI conference in Atlanta. On keys of 5.3 by 5.8 centimeters, users mistyped 3 percent of letters. On the smallest keys, 1.1 by 1.7 centimeters, the error rate was 28.6 percent. The prototype measured less than one square meter and held about one person.

The floor worked; what it never found was a room that needed it.

From one square meter to a room

The team planned a larger unit of 3 by 2.15 meters, weighing 1.2 metric tons, for a new building at the institute, and published the full paper at ACM UIST 2010. PCWorld noted that there was no word on whether Multitoe would ever be commercialized.

It was not. The floor became lab equipment. In 2013 the group presented GravitySpace on an 8 square meter version, about ten times the size of the first one. It worked out where people and furniture were, and what pose a person was in, from the pressure imprints they left. In 2014 came Kickables, objects that visitors push around with their feet, shown with a prototype museum exhibit on molecular chemistry. The lab’s recent projects are mostly about personal fabrication.

What it means now

A glass floor with cameras and projection below it is hard to fit into a building. The floors that did get installed do less. SensFloor, from the German company Future-Shape, is a 2-millimeter textile underlay with capacitive sensors that goes under ordinary flooring. Core77 reported in 2014 that a nursing home in Alsace used it to detect falls. Interactive play floors such as EyeClick’s BEAM turn the setup upside down: projector and motion sensor are mounted above the floor.

What Multitoe showed is that feet are better pointers than they look. A sole can identify its owner, and a foot can hit a target much smaller than itself. At the desk, feet are still used in the plainest way, as pedals. The floor that knows who is standing on it remains a research result.