Search Results

Now showing 1 - 9 of 9
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    State of the Art Non-Photorealistic Rendering (NPR) Techniques
    (The Eurographics Association, 2006) Sayeed, Rezwan; Howard, Toby; Louise M. Lever and Mary McDerby
    The emergence of non-photorealistic rendering (NPR) over the greater part of a decade has created an intriguing new field espousing expression, abstraction and stylisation in preference to the traditional computer graphics concerns for photorealism. By lifting the burden of realism, NPR is capable of engaging with users, providing compelling and unique experiences through devices such as abstraction and stylisation. Many artistic and visual styles have been achieved by NPR including interactive and automated systems for drawing and painting. In this paper we outline the current state-of-the-art of NPR for visualisation and identify some current and future trends in NPR research.
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    Book Reviews
    (Blackwell Publishers Ltd and the Eurographics Association, 1997) Howard, Toby
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    Automatically Generating Virtual Humans using Evolutionary Algorithms
    (The Eurographics Association, 2009) Albin-Clark, Adrian; Howard, Toby; Wen Tang and John Collomosse
    Abstract Virtual Humans are used in many applications either as an embodiment of a real person (an "avatar"), or under the control of a computer program (an "agent" or "non-player character"). The automatic generation of Virtual Humans is a challenging problem if they are to look both plausible and unique within a population. We present an approach which exploits the power of Evolutionary Algorithms (EAs), and provide illustrative examples of how our methods may be realised within the context of surface-based model geometry.
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    A View of Eurographics 87
    (Blackwell Publishing Ltd and the Eurographics Association, 1987) Howard, Toby
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    Rapid Shadow Generation in Real-World Lighting Environments
    (The Eurographics Association, 2003) Gibson, Simon; Cook, Jon; Howard, Toby; Hubbold, Roger; Philip Dutre and Frank Suykens and Per H. Christensen and Daniel Cohen-Or
    We propose a new algorithm that uses consumer-level graphics hardware to render shadows cast by synthetic objects and a real lighting environment. This has immediate benefit for interactive Augmented Reality applications, where synthetic objects must be accurately merged with real images. We show how soft shadows cast by direct and indirect illumination sources may be generated and composited into a background image at interactive rates. We describe how the sources of light (and hence shadow) affecting each point in an image can be efficiently encoded using a hierarchical shaft-based subdivision of line-space. This subdivision is then used to determine the sources of light that are occluded by synthetic objects, and we show how the contributions from these sources may be removed from a background image using facilities available on modern graphics hardware. A trade-off may be made at runtime between shadow accuracy and rendering cost, converging towards a result that is subjectively similar to that obtained using ray-tracing based differential rendering algorithms. Examples of the proposed technique are given for a variety of different lighting environments, and the visual fidelity of images generated by our algorithm is compared to both real photographs and synthetic images generated using non-real-time techniques.
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    MAVERIK: A Virtual Reality System for Research and Teaching
    (The Eurographics Association, 2023) Howard, Toby; Hubbold, Roger; Murta, Alan; José Carlos Teixeira; Werner Hansmann; Michael B. McGrath
    This paper describes some experiences with the use of the MAVERIK system for supporting undergraduate and postgraduate teaching and research. MAVERIK is a high-level system for creating and managing interactive virtual environments. lt is available free under the GNU General Public Licence. MAVERIK is modular and extensible, and its use of Mesa, the free OpenGL-like graphics system, means that it can be run on low- cost PCs, making it especially suitable for use in computer graphics and visualization education. We discuss the novel architecture and main features of MAVERIK, and illustrate its use by presenting case studies of projects udertaken by our students.
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    Flexible Image-Based Photometric Reconstruction using Virtual Light Sources
    (Blackwell Publishers Ltd and the Eurographics Association, 2001) Gibson, Simon; Howard, Toby; Hubbold, Roger
    Photometric reconstruction is the process of estimating the illumination and surface reflectance properties of an environment, given a geometric model of the scene and a set of photographs of its surfaces. For mixed-reality applications, such data is required if synthetic objects are to be correctly illuminated or if synthetic light sources are to be used to re-light the scene. Current methods of estimating such data are limited in the practical situations in which they can be applied, due to the fact that the geometric and radiometric models of the scene which are provided by the user must be complete, and that the position (and in some cases, intensity) of the light sources must also be specified a-priori. In this paper, a novel algorithm is presented which overcomes these constraints, and allows photometric data to be reconstructed in less restricted situations. This is achieved through the use of virtual light sources which mimic the effect of direct illumination from unknown luminaires, and indirect illumination reflected off unknown geometry. The intensity of these virtual light sources and the surface material properties are estimated using an iterative algorithm which attempts to match calculated radiance values to those observed in photographs. Results are presented for both synthetic and real scenes that show the quality of the reconstructed data and its use in off-line mixed-reality applications.
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    Book Reviews
    (Blackwell Publishers Ltd and the Eurographics Association, 2002) Howard, Toby
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    A Shareable Centralised Database of KRT3 - A Hierarchical Graphics System Based on PHIGS
    (Eurographics Association, 1987) Howard, Toby
    The Programmer’s Hierarchical Interactive Graphics System (PHIGS), currently under development by ISO, is a specification of a set of functions for device-independent computer graphics programming, supporting dynamic interaction and hierarchically organised graphical data. A central aspect of an implementation of a system such as PHIGS is the provision of a compact and efficient representation for the graphical entities involved. This paper describes a centralised graphical database for KRT³, an experimental hierarchical graphics system based on PHIGS. It presents a discussion of the issues involved, and the experience gained, in the practical design and implementation of a database for hierarchical graphical data. A novel aspect of the design is that the database may be simultaneously shared by several application programs.