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Item Piecewise Constant Conic Sections for Accelerated Volume Density Rendering(Eurographics Association, 2001) Hougs, Roland B.; Day, A. M.In order to accelerate the rendering of volumetric shadows, we propose a new technique which builds sets of conic volumes to approximate the shape of shadows in a participating medium. The novelty of our approach is notably the construction of the cone-sets, which are built with no knowledge of the underlying geometry of the scene. Instead, information collected during the construction of a global photon map is used to derive an estimate of the outline of the shadows in three dimensions. This information is then used in several different ways to speed up the rendering pass. The method shares many of the advantages proposed by photon maps such as viewpoint independence and decoupling from the geometry of the scene.Item The Norwich Virtual City Project(Eurographics Association, 1999) Arnold, D. B.; Day, A. M.This paper describes the early work on implementing a visitor attraction based on the heritage of the Norwich area. The project has been in planning for about three years, but has only just been funded and is due to open in 2001. The paper reviews the background to the project and the city, and considers the expected benefits of the venture. The range of data sources are then reviewed and areas are highlighted where computer science research needs to progress to maximise benefits. The paper then reviews progress to date on the project.Item Fast Hierarchical Methods to Detect Collisions between Deformable Objects: A Comparison(The Eurographics Association, 2007) Madera, Francisco; Day, A. M.; Laycock, S. D.; Paolo Cignoni and Jiri SochorThe time complexity of a collision detection algorithm can be reduced to logarithmic in the number of tests performed when the objects are decomposed into a Bounding Volume (BV) tree hierarchy. It is well known that the Sphere Bounding Volume (SBV) and the Axis Aligned Bounding Box (AABB) hierarchies require inexpensive overlapping tests. However, we present a method called the Distance Hierarchy (DH) which is more suitable for deformable objects and is very simple to implement. It uses a hierarchical tree to decompose each object into regions. Each region requires just one parameter, its radius. In this work we compare three methods, AABB hierarchy, Sphere hierarchy, and DH, where the focus is on the intersection test, computation time, and the use of memory.Item High Quality Shadows for Real-Time Crowds(The Eurographics Association, 2006) Ryder, G.; Day, A. M.; Dieter Fellner and Charles HansenReal-time shadowed crowds, especially under locally lit environments, pose several distinct challenges. Current solutions for crowds are either very simplistic for multiple lights or only handle a single directional light with shadows. This work focuses on bringing hundreds of local lights with high fidelity shadows for crowds into the real-time domain. Each light is given the ability to cast shadows for all objects (dynamic and static) within the scene, and all the levels of detail used for representing the crowds correctly interact with the lighting conditions. In this paper we introduce depth augmented billboards for crowds, to allow for improved quality under local lights, including self-shadowing. Through use of the GPU fragment programs; this extension is entirely implemented on the graphics card for minimal performance impact.Item Distributed Virtual Environments for Urban Modelling(Eurographics Association, 1999) Harvey, D.; Arnold, D. B.; Day, A. M.We describe many of the considerations required when designing and developing a distributed virtual environment for urban modelling, paying particular attention to its application to virtual heritage. We also describe the possibility of using a specially defined set of scenery and building primitives to reduce the amount of data that needs to be transmitted to recreate the virtual urban environment on the observer’s computer.Item Rapid Urban Modelling(Eurographics Association, 1999) Cooper, J. W.; Arnold, D. B.; Day, A. M.We describe a system that allows the rapid creation of virtual urban models. We describe how this system can extract 3D model information from Ordnance Survey maps by using a rule-based modelling approach and a parameterised description for common buildings. We also give ideas about how this system could be extended to add detail to models generated from aerial photographs and to include historical events within the model. Finally we show how the models can support changes in level of detail and compression.