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Item A Survey of Haptic Rendering Techniques(The Eurographics Association and Blackwell Publishing Ltd, 2007) Laycock, S.D.; Day, A.M.Computer Graphics technologies have developed considerably over the past decades. Realistic virtual environments can be produced incorporating complex geometry for graphical objects and utilising hardware acceleration for per pixel effects. To enhance these environments, in terms of the immersive experience perceived by users, the human s sense of touch, or haptic system, can be exploited. To this end haptic feedback devices capable of exerting forces on the user are incorporated. The process of determining a reaction force for a given position of the haptic device is known as haptic rendering. For over a decade users have been able to interact with a virtual environment with a haptic device. This paper focuses on the haptic rendering algorithms which have been developed to compute forces as users manipulate the haptic device in the virtual environment.Item Siggraph 2006 Boston, Massachusetts, 30th July-3rd August 2006(The Eurographics Association and Blackwell Publishing Ltd, 2007) Laycock, R.G.; Laycock, S.D.; Ryder, G.; Day, A.M.Item The Implementation of a 2D Convex Hull Algorithm Using Perturbation(Blackwell Publishing Ltd and the Eurographics Association, 1990) Day, A.M.This paper discusses the problem of geometric degeneracies and outlines possible solutions when converting geometric algorithms into practice. It concentrates on the application of one of the suggested solutions, a perturbation technique, to a 2D convex hull program. An outline of the relevant theory and its conversion into practice is given. Experimental results are presented and discussed.Item A Key-Pose Caching System for Rendering an Animated Crowd in Real-Time(The Eurographics Association and Blackwell Publishing Ltd, 2010) Lister, W.; Laycock, R.G.; Day, A.M.We present a method to accelerate the visualization of large crowds of animated characters. Linear-blend skinning remains the dominant approach for animating a crowd but its efficiency can be improved by utilizing the temporal and intra-crowd coherencies that are inherent within a populated scene. Our work adopts a caching system that enables a skinned key-pose to be re-used by multi-pass rendering, between multiple agents and across multiple frames. We investigate two different methods; an intermittent caching scheme (whereby each member of a crowd is animated using only its nearest key-pose) and an interpolative approach that enables key-pose blending to be supported. For the latter case, we show that finding the optimal set of key-poses to store is an NP-hard problem and present a greedy algorithm suitable for real-time applications. Both variants deliver a worthwhile performance improvement in comparison to using linear-blend skinning alone.Item Accelerated Artificial Landscape Visualisation(Eurographics Association, 1999) James, A.; Day, A.M.We describe the design and implementation of four stages in an artificial landscape visualisation program. We begin by outlining a very simple but quick method of generating structurally realistic landscapes. We describe how the terrain can be stored in a multiresolution Binary Space Partitioning (MRBSP) tree such that each level holds a complete representation of the terrain at increasing reso- lution. A level of detail (LOD) technique is then illustrated which preserves the visually apparent size of triangles (after projection) so that the number rendered is reduced while preserving the aesthetic quality. Finally, we show how visibility calculations can be preprocessed and used to achieve output sensitivity by limiting the observer to ground based motion.Item Improved Visualisation of Marine Data: Algae and Acid Rain(Blackwell Science Ltd and the Eurographics Association, 1994) Day, A.M.; Turner, S.M.; Arnold, D.B.Item The Hidden Face Determination Tree(Eurographics Association, 1998) James, A.; Day, A.M.Hidden surface removal can be achieved using the Priority Face Determination (PFD) tree to create a priority ordering of n polygons in log4=3 n time. In this paper, we describe the Hidden Face Determi- nation (HFD) tree which is based upon the PFD tree. The HFD tree is constructed in a similar way as the PFD tree, but an addition means that polygons completely hidden by others in the scene can be determined at each node. Thus, not only does the HFD tree calculate the priority order of polygons in log4=3 n time, but determines which polygons are invisible from a given location.Item Experiments in the Parallel Computation of 3D Convex Hulls(Blackwell Science Ltd and the Eurographics Association, 1994) Claret, A.R.; Day, A.M.Two parallel implementations of a 3D convex hull algorithm are reported. The paper considers a MIMD distributed memory architecture and the implementations are carried out on the Meiko Computing Surface using T800 transputers and the programming languages Occam and C. The first method uses a simple parallel geometric decomposition strategy and produces encouraging results. With the second approach a parallel generic Divide-and-Conquer kernel is incorporated. This is an example of the algorithmic skeleton approach to parallel programming and involves run-time, dynamic allocation of work to processors. The resulting performances for both methods are measured and compared.Item Siggraph 2005 Los Angeles, California, 31st July-4th August 2005(The Eurographics Association and Blackwell Publishing Ltd., 2005) Laycock, S.D.; Laycock, R.G.; Day, A.M.Item Conflict Neutralization on Binary Space Partitioning(Blackwell Publishers Ltd and the Eurographics Association, 2000) James, A.; Day, A.M.The Binary Space Partitioning (BSP) tree achieves fast hidden surface removal for most practical applications where an observer can move through a scene of static objects. However, the BSP algorithm generally increases the number of polygons in a scene due to its splitting stage resulting in a detrimental effect on the priority ordering and more significantly, the display calculations (shading, lighting, shadows, etc.) of the rendering pipeline.We present the Conflict Neutralization algorithm which attempts to reduce the number of splits more effectively than existing techniques whilst maintaining the 'standard' model of a BSP tree. Our idea is similar to Conflict Minimization proposed by Fuchs; the significant difference is that our algorithm recognizes that a polygon suitable for selection in the Minimization criterion may subsequently stop the remainder of polygons achieving some reductions in cuts-with Conflict Neutralization, such a polygon is demoted.We compare the results of Conflict Neutralization against Conflict Minimization, the Least-crossed with Most-crossed tie-breaking criterion and our own, enhanced implementation of Conflict Minimization. We show how these techniques fall into different 'depths of analysis'.