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BlackMagic

BlackMagic is an interactive tabletop that works by liquid displacement inside a malleable projection surface. The system provides both touch and pressure information and a distinct organic quality when touched. The system is easy to build and produces a clean signal revealing multiple fingers, whole hands and other object outlines that can be processed using computer vision techniques. This approach provides an easy mechanism to build interactive surfaces, requiring no infrared edge lighting or soldering.

Liquid Displacement Sensing

The core of the touch sensor is a pouch made of a acrylic plate and a sheet of white latex rubber which serves both as projection screen and transducer for user input. The pouch is filled with a mixture of water and black ink which hides the white latex surface from the camera beneath the acrylic plate when nothing touches the surface. Touching objects displace the liquid and press the latex onto the transparent plate. This reveals the shape of the touching object in bright white through to the camera.

Basic Setup

In our prototype we used an 800x600mm, 5mm thick sheet of acrylic. Black liquid is poured onto this surface, and white latex rubber (approx. 0.4mm thick), silicone sealant and an alloy frame are used to form a pouch to contain the liquid and stop it from leaking. This panel rests on a black painted wooden frame. In addition to four table legs two visible light sources are attached to the bottom of the frame. The light sources serve to increase the contrast of the sensor image in low light conditions. The camera is placed between the table legs so that it captures the whole panel. The screen image is projected by a projector on the white latex rubber which is mounted above the interactive surface.

Surface Material Properties

Due to the organic quality of the materials the interactive surface can be adapted for different purposes. This can be done through the variation of the material properties like surface malleability and tension, liquid viscosity, tint and opacity, and the internal pressure of the pouch. For instance, a panel with increased volume which is filled with semi-transparent tinted liquid can be used to acquire more detailed depth-based contours compared to a panel which is filled with completely opaque black ink.

The BrainStorm is also presented in a short Video.