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Fast and Accurate Input Handling for Optical Surfaces

This is an ongoing project.


EquisFtir is a construction method for multitouch tabletop surfaces together with an open source library for using such tabletops to build XNA Studio games. We have developed EquisFtir within our tabletop gaming project. For examples of its use, see our Asterocks game.

The total cost of the components required to build the EquisFtir table is approximately $1,000-$2,000, far less than commercial tables. This makes tabletops accessible to research labs, and, pending commoditization, within plausible price range for home use. We are designing an improved version of our table to support research in other laboratories; for progress see Chris Wolfe’s blog.


EquisFtir interacts with a tabletop surface and a game application. Grayscale bitmaps representing IR intensity are retrieved from from the camera. The library tracks intensity changes from frame to frame, and uses them to identify the movement of “blobs” around the table. Blobs are simply pools of light, generated by users adding, removing or dragging objects around the table. These “objects” are typically fingers, but we have successfully captured the use of other objects such as cookie cutters or even a paintbrush on the tabletop. EquisFtir deals well with noisy input, as areas that are statically bright due to other IR light sources will not generate inputs.

EquisFtir has very modest hardware requirements, making it practical to run all but the most demanding of games on the same computer as the image image processing library.

The EquisFtir library is used within Microsoft’s XNA Studio, a freely available environment supporting the development of 2D and 3D games. XNA Studio is compatible with PCs, the Xbox 360, the Zune, and now, FTIR tabletops.



This Alpha release supports limited hardware and has several known bugs. While we have used it successfully for informal experiments and demonstrations, the toolkit is far from complete. For details see the documentation and demos within the distribution. Copyright © 2008-2010 Christopher Wolfe

EquisFtir is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

EquisFtir is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.