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Recent Submissions

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    Effects of target size and distance on kinematic endpoint prediction
    (University of Waterloo, 2009-09-25) Ruiz, Jaime; Lank, Edward
    Because of the ubiquity of the WIMP paradigm, many researchers seek to design new pointing facilitation techniques for Fitts-style pointing tasks. However, many of these pointing facilitation techniques make one of two simplifying assumptions: either salient targets are sparsely placed on the display, or there exists some ability to identify the endpoint, the target, of a user's movement in real time. In this paper we extend previous work on kinematic endpoint prediction (KEP), a technique that uses models of user motion to predict endpoint in Fitts-style pointing tasks. We introduce a simplified algorithm to predict user endpoint. We present a technique to measure the numerical stability of endpoint predictions in real time. We show that the distance of motion has a significant effect on predictor accuracy. Finally, we develop an accurate understanding of the relationship between movement distance and predictor accuracy and show how we can use this understanding to infer accurate, real-time probability distributions on target sets within an interface. Together, these results allow KEP to be applied in new and novel ways to pointing facilitation techniques.
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    Approximation of generalized processor sharing with interleaved stratified timer wheels - Extended version
    (University of Waterloo, 2009-09-17) Karsten, Martin
    This paper presents Interleaved Stratified Timer Wheels as a novel priority queue data structure for traffic shaping and scheduling in packet-switched networks. The data structure is used to construct an efficient packet approximation of General Processor Sharing (GPS). This scheduler is the first of its kind by combining all desirable properties without any residual catch. In contrast to previous work, the scheduler presented here has constant and near-optimal delay and fairness properties, and can be implemented with O(1) algorithmic complexity, and has a low absolute execution overhead. The paper presents the priority queue data structure and the basic scheduling algorithm, along with several versions with different cost-performance trade-offs. A generalized analytical model for rate-controlled rounded timestamp schedulers is developed and used to assess the scheduling properties of the different scheduler versions. Some illustrative simulation results are presented to reaffirm those properties.
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    An evaluation of shape/split grammars for architecture
    (University of Waterloo, 2009-08-17) Huang, Jingyuan; Pytel, Alex; Zhang, Cherry; Mann, Stephen; Fourquet, Elodie; Hahn, Marshall; Kinnear, Kate; Lam, Michael; Cowan, William
    Shape grammars have been used as a method for modelling buildings, both in architecture and in computer graphics. In this report, we survey some of the shape grammar papers, present some projects using shape grammars, and give our evaluation of shape grammars in computer graphics. In particular, we feel shape grammars are useful for generating a large variety of buildings, such as might be needed in computer games or animations, and that they could also be useful in design for exploring a large number of similar variations. However, we feel they are less useful for the design of new buildings or modelling of existing buildings.
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    A survey of incentive mechanisms in peer-to-peer systems
    (University of Waterloo, 2009-06-16) Rahman, Muntasir Raihan
    The fundamental assumption that peer-to-peer (P2P) networks can thrive on voluntary contribution of altruistic peers can no longer be supported without considering the impact of rational behaviour on such decentralized systems. This paper attempts to shed light on the impact of rational free-riding behaviour of participating peers on the stability and existence of real-world peer-to-peer networks and the various attempts to cope with this problem. In particular, we focus on the economic principles that drive these problems, the various incentive mechanisms proposed to thwart these problems and analytical tools used to describe these rational manipulations in P2P systems.
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    Using A-patches to tessellate algebraic curves and surfaces
    (University of Waterloo, 2009-06-11) Mann, Stephen
    This technical report expands on the A-patch tessellation work in the masters thesis of Curtis Luk [Luk08], improving on many of the techniques in his work and extending the A-patch constraints to allow a wider class of single sheeted Bernstein representations.