Department of Computer Science and Technology

Technical reports

Computing surfaces – a platform for scalable interactive displays

Alban Rrustemi

November 2008, 156 pages

This technical report is based on a dissertation submitted November 2008 by the author for the degree of Doctor of Philosophy to the University of Cambridge, St Edmund’s College.

DOI: 10.48456/tr-732


Recent progress in electronic, display and sensing technologies makes possible a future with omnipresent, arbitrarily large interactive display surfaces. Nonetheless, current methods of designing display systems with multi-touch sensitivity do not scale. This thesis presents computing surfaces as a viable platform for resolving forthcoming scalability limitations.

Computing surfaces are composed of a homogeneous network of physically adjoined, small sensitive displays with local computation and communication capabilities. In this platform, inherent scalability is provided by a distributed architecture. The regular spatial distribution of resources presents new demands on the way surface input and output information is managed and processed.

Direct user input with touch based gestures needs to account for the distributed architecture of computing surfaces. A scalable middleware solution that conceals the tiled architecture is proposed for reasoning with touch-based gestures. The validity of this middleware is proven in a case study, where a fully distributed algorithm for online recognition of unistrokes – a particular class of touch-based gestures – is presented and evaluated.

Novel interaction techniques based around interactive display surfaces involve direct manipulation with displayed digital objects. In order to facilitate such interactions in computing surfaces, an efficient distributed algorithm to perform 2D image transformations is introduced and evaluated. The performance of these transformations is heavily influenced by the arbitration policies of the interconnection network. One approach for improving the performance of these transformations in conventional network architectures is proposed and evaluated.

More advanced applications in computing surfaces require the presence of some notion of time. An efficient algorithm for internal time synchronisation is presented and evaluated. A hardware solution is adopted to minimise the delay uncertainty of special timestamp messages. The proposed algorithm allows efficient, scalable time synchronisation among clusters of tiles. A hardware reference platform is constructed to demonstrate the basic principles and features of computing surfaces. This platform and a complementary simulation environment is used for extensive evaluation and analysis.

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BibTeX record

  author =	 {Rrustemi, Alban},
  title = 	 {{Computing surfaces -- a platform for scalable interactive
  year = 	 2008,
  month = 	 nov,
  url = 	 {},
  institution =  {University of Cambridge, Computer Laboratory},
  doi = 	 {10.48456/tr-732},
  number = 	 {UCAM-CL-TR-732}