Issue 5

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https://diglib.eg.org/handle/10.2312/64

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    A Constraint-Based Reasoning Framework for Behavioural Animation
    (Blackwell Science Ltd and the Eurographics Association, 1994) Mah, Sang; Calvert, Thomas W.; Havens, William
    Behaviour is a reflection of a reasoning process that must deal with constraints imposed by an external environment, internal knowledge and physical structure. This paper proposes a framework for behavioural animation that is based on the next generation of object-oriented, constraint-based expert systems technology, and applies a control structure of knowledge agents and knowledge units to determine the behaviour of objects to be animated. Knowledge agents are responsible for planning, plan implementation and information extraction from the environment. The activity of an agent is dependent on the knowledge units ascribed to them by the animator. The interaction between agents and knowledge units is resolved by the reasoning engine, and thus, influences the eventual motion displayed. An example given is NSAIL, a pilot implementation using the model-based ECHIDNA constraint logic programming shell. With this approach, the motion for a sailing scenario and other behavioural domains can be specified at a high level through the characterization of the knowledge agents.
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    Contextual Animation of Gestural Commands
    (Blackwell Science Ltd and the Eurographics Association, 1994) Kurtenbach, G.; Moran, T. P.; Buxton, W.
    Drawing a mark can be an efficient command input technique when using a pen-based computer. However, marks are not intrinsically self-explanatory as are other interactive techniques such as buttons and menus. We present design principles for interaction mechanisms which make marks self explanatory for novices but still allow experts to use efficient command marks. The key notion is that use of the explanation mechanism physically trains a novice to use the efficient command marks. Two novel interaction mechanisms we have developed using these principles are presented.
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    Multiresolution Tiling
    (Blackwell Science Ltd and the Eurographics Association, 1994) Meyers, David
    This paper describes an efficient method for constructing a tiling between a pair of planar contours. The problem is of interest in a number of domains, including medical imaging, biological research and geological reconstructions. Our method, based on ideas from multiresolution analysis and wavelets, requires O(n) space and appears to require O(n log n) time for average inputs, compared to the O(n2) space and O(n2 log n) time required by the optimizing algorithm of Fuchs, Kedem and Uselton1. The results computed by our algorithm are in many cases nearly the same as those of the optimizing algorithm, but at a small fraction of the computational cost. The performance improvement makes the algorithm usable for large contours in an interactive system. The use of multiresolution analysis provides an efficient mechanism for data compression by discarding wavelet coefficients smaller than a threshold value during reconstruction. The amount of detail lost can be controlled by appropriate choice of the threshold value. The use of lower resolution approximations to the original contours yields significant savings in the time required to display a reconstructed object, and in the space required to store it.
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    A New Real Time Geometric Transformation Matrix and its Efficient VLSI Implementation
    (Blackwell Science Ltd and the Eurographics Association, 1994) Ng, C. M.; Bustard, D. W.
    The geometric transformation of an image with irregular shapes from a source space to a target space requires a huge number of multiplications and additions for each pixel. Such a through put is impossible to deliver by any processor in real-time. This paper presents a new transformation matrix which can be used toper form real-time 2-D geometric transformations economically. The implementation of the transformation engine that is used to execute the transformation matrix is also presented. Experimental results indicate that real-time geometric transformations based on a 4 ? 4 transformation mesh can be achieved with the use of the transformation engine. This real-time transformation function is useful in warping and blending of images, and can be easily extended to perform irregular shape transformations with a large number of control points in the transformation mesh.
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    A Schematic Entry Drawing Capability in a Linearised Hypermedia System
    (Blackwell Science Ltd and the Eurographics Association, 1994) Benest, I. D.
    This paper describes a linearised hypermedia system, called the Book Emulator, that generally supports the capture of diagrammatic specifications such as SSADM and electronic circuit diagrams, and the capture of mathematical notations such as Z. Since the Book Emulator can be closely coupled to applications, it can be used as the user-interface to that application. Doing so automatically provides a conferencing mechanism on behalf of applications and a mechanism for recording the engineering analyses performed by the application. It is argued that this is the next and higher step in the trend to separate the user-interface from the application. The schematic entry mechanism has been designed to minimise the user s physical and mental effort so that the user may concentrate on drawing strategy. This is achieved by minimising the number of selections (steps) required to reach an atomic goal, and by refraining from hiding functionality in menus. The paper concludes with an indication of how the generalised schematic capture mechanism might be exploited in systems that allow end- users to organise and specify their information requirements.