EG UK Theory and Practice of Computer Graphics 2008
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Item A Benchmarking Framework for Static Collision Detection(The Eurographics Association, 2008) Diktas, Engin Deniz; Sahiner, Ali Vahit; Ik Soo Lim and Wen TangPerformanceof static collision detection queries depends on the type of the hierarchy chosen as well as the relative positioning of the colliding objects. In order to evaluate the performance of bounding volume hierarchies, relevant criteria that affect the query performance need to be determined and the sample space should be generated accordingly. In this paper we present a benchmarking framework for evaluating the performance of various static collision detection algorithms. In this framework, instances of a moving rigid object are placed on the surface of another instance of the same object fixed at a certain position, where the contact occurs for the first time. Then by offsetting the surface inwards (outwards) we generate new surfaces that are at a certain fixed negative (positive) distance to the original surface. Placing the moving object on these offset surfaces makes the object penetrate (approach) the fixed object at a fixed distance. For offset surface generation we create a signed distance field and run marching cubes algorithm on it.Item Contouring with Uncertainty(The Eurographics Association, 2008) Osorio, R. S. Allendes; Brodlie, K. W.; Ik Soo Lim and Wen TangThe visualization of uncertainty remains one of the major challenges for the visualization community. To achieve this, we need to understand and develop methods that allow us not only to consider uncertainty as an extra variable within the visualization process, but to treat it as an integral part. In this paper, we take contouring, one of the most widely used visualization techniques for two dimensional data, and focus on extending the concept of contouring to uncertainty. We develop special techniques for the visualization of uncertain contours. We illustrate the work through application to a case study in oceanography.Item Efficient Path Matching Motion Generation Algorithm for Multi Agent Environment(The Eurographics Association, 2008) Lau, Newman; Chow, Chapmann; Lee, Pouro; Iu, Bartholomew; Ik Soo Lim and Wen TangThis paper presents an efficient method to generate a large amount of continuous motion data from motion captured data. Given user defined way point lists for each agent, the algorithm can automatically generate collision free walking paths for them. The walking path data is then analyzed and transformed into a sequence of agent states such as walking or standing state. Based on the randomized depth first algorithm, the agent states are matched with a sequence of corresponding motion clips. The final motion is obtained by blending the motion clips to fit with the speed of the agents' walking paths. From our experiments, our algorithm generates natural looking motions.Item Efficient Representation of Layered Depth Images for Real-time Volumetric Tests(The Eurographics Association, 2008) Trapp, Matthias; Döllner, Jürgen; Ik Soo Lim and Wen TangRepresenting Layered Depth Images (LDI) as 3D texture can be used to approximate complex, arbitrarily shaped volumes on graphics hardware. Based on this concept, a number of real-time applications such as collision detection or 3D clipping against multiple volumes can be implemented efficiently using programmable hardware. One major drawback of this image-based representation is the high video memory consumption. To compensate that disadvantage, this paper presents a concept and associated algorithms that enable a lossless, efficient LDI representation which is especially designed for the usage within shader programs. The concept comprises the application of a viewpoint selection, a cropping, and a compression algorithm. We evaluated our algorithm with different test cases and show possible use cases.Item A Fast Algorithm for Painterly Rendering on Mobile Devices(The Eurographics Association, 2008) Mukundan, R.; Han, C.; Ik Soo Lim and Wen TangWith the rapid growth of mobile graphics applications, non-photorealistic rendering algorithms developed particularly for devices with limited processor capabilities have become important in the areas of games design and augmented reality. This paper presents a fast painterly rendering algorithm suitable for implementation on mobile phones. Connected components in an image are identified and stored in an index buffer, using a sequential scan. Most of the subsequent processing is done only on this index buffer that contains one integer value per pixel. The proposed method does not use recursive procedures, complex floating-point computations, or texture processing functions. The painterly rendered effect is produced by suitably modifying the boundary of connected components and highlighting edges using entries from the index buffer. The paper presents the theoretical framework for the algorithm, implementation aspects and results.Item Game-Based Training in an Interactive Environment by means of OpenCrimeScene(The Eurographics Association, 2008) Brennecke, Angela; Schlechtweg, Stefan; Schumann, Heidrun; Ik Soo Lim and Wen TangThis paper presents a novel approach towards training with game elements in an interactive environment by means of OpenCrimeScene, a virtual 3D training system for crime scene investigation (CSI). The application is designed to supplement the curriculum for self-study and as a basis for group discussion. To facilitate curriculum integration, the interactive environment has been made suitable for distinct audience groups (i. e. teachers and students). Different interaction techniques for each group have been developed respectively. The application consists of three main components which are called authoring, training, and reviewing. The underlying application framework follows a generic approach and can also be adapted to training fields other than CSI.Item Generation and Tessellation of Tree Stems(The Eurographics Association, 2008) Skjermo, Jo; Ik Soo Lim and Wen TangWhen visualizing tree stems and branches for use in interactive applications, the polygon models resolution are usually as low as possible to achieve a high frame rate. Also, to ease animation and mesh generation, each branch of a tree model is often considered as a distinct mesh. However, by using a single watertight mesh for a tree, together with (GPU-based) tessellation, both the resolution and appearance of a tree can be greatly improved while maintaining a high frame rate. This paper presents concepts, ideas and early work on generating watertight polygon meshes of animated trees stems suitable for refinement and tessellation of such meshes.Item GPU-based Visualisation of Protein Secondary Structure(The Eurographics Association, 2008) Krone, Michael; Bidmon, Katrin; Ertl, Thomas; Ik Soo Lim and Wen TangThe increasing number of protein 3D structure information available makes the high-quality visualisation of this information play a more and more important role. Beside element-based representations the secondary-structurebased representation - also called cartoon representation - refers to a higher level of abstraction, representing the protein structure as tubes and ribbons. We present a method for this cartoon representation of proteins using the ability of modern graphics hardware's geometry shaders and thus reducing the amount of data to be transferred from the CPU to the graphics card. The resulting minimisation of storage needed is of particular importance when dealing with huge datasets. High-quality images at interactive frame rates can thus be achieved.Item Grammatical Evolution for Gait Retargeting(The Eurographics Association, 2008) Murphy, James E.; Carr, Hamish; O'Neill, Michael; Ik Soo Lim and Wen TangArtists and scientists require tools to construct physics-based animal models. However, animating these models requires motion data for realistic movement. Motion data may either be measured from real-life animals-in-motion or generated using an optimisation approach. We propose a solution for retargeting gait data from one animal to another. The retargeted gait cycles are generated using a Grammatical Evolution optimisation approach and the search space is constrained based on dynamic similarity principles.Item A Haptic Rendering Algorithm for Drilling into Volume Data(The Eurographics Association, 2008) Liu, Yu; Laycock, S. D.; Ik Soo Lim and Wen TangWith the developments of volume visualisation technology for complex data sets comes new challenges in terms of user interaction and information extraction. Volume haptics has proven itself to be an effective way of extracting valuable information by providing an extra sense from which to perceive three dimensional data. In this paper, a novel indirect haptic rendering method using a Marching Cubes algorithm is presented for volume data removal. A novel three-step haptic rendering method is presented, which can be used to provide continuous and smooth force feedback during the drilling of various types of volumetric data.Item Image Abstraction by Structure Adaptive Filtering(The Eurographics Association, 2008) Kyprianidis, Jan Eric; Döllner, Jürgen; Ik Soo Lim and Wen TangIn this work we present a framework of automatic non-photorealistic image processing techniques that create simplified stylistic illustrations from color images, videos and 3D renderings. To smooth low-contrast regions while preserving edges, we present a new fast separated implementation of the bilateral filter. Our approach works by filtering in direction of the gradient and then filtering the intermediate result in perpendicular direction. When applied iteratively, our approach does not suffer from horizontal or vertical artifacts and creates smooth output at curved boundaries. To extract salient important edges we first apply a one-dimensional difference-of-Gaussians filter in direction of the gradient and then apply smoothing along a flow field which we derive from the smoothed structure tensor. Our method creates smooth coherent output for line and curve segments.Item Interactive Grid Based Binning for Information Visualization(The Eurographics Association, 2008) Longshaw, S. M.; Turner, M. J.; Hewitt, W. T.; Ik Soo Lim and Wen TangClutter within information visualization (infovis) systems is an area of continuing concern and is receiving increasing research interest. Solutions to the problem vary in their approach, ranging from novel visualizations designed specifically to cope with high data density, through to statistical methodologies such as binning. This paper presents a flexible method that allows interactive placement of a grid based binning system that aims to enhance traditional information visualization techniques. User evaluations employing two specific visualization methods are described using a prototype grid based binning system. The method is shown to be a quick and easy way to visually segment a data domain, while the two visualization techniques presented are shown to provide effective data overview. Due to the abstracted nature of the binning grid, its applicability goes beyond the examples provided in this paper, therefore it could be considered as a generic data reduction and/or overview technique within many systems.Item Interactive Out-of-Core Exploration of Large Volume Datasets in VTK-Based Visualisation Systems(The Eurographics Association, 2008) Agrawal, A.; Kohout, J.; Clapworthy, G. J.; McFarlane, N. J. B.; Dong, F.; Viceconti, M.; Taddei, F.; Testi, D.; Ik Soo Lim and Wen TangThe Visualisation ToolKit (VTK) has become a very popular tool for scientific data visualisation and it is used as a base in many existing visualisation systems. Scientific datasets produced nowadays by complex scientific simulations or by modern data acquisition techniques (e.g., airborne laser scanning) are often too large to be processed in one piece on commodity hardware, as simply storing it requires several giga-bytes. Although VTK provides a means for processing such datasets, their straightforward use is rarely efficient. This paper describes an efficient interactive exploration of large volume datasets under the Multimod Application Framework (MAF) [VZT*07], a VTK-based system; however, the proposed approach can be adopted for other systems with ease. It exploits various techniques such as multi-resolution layout and a volume bricking scheme to access data at an interactive rate. A user can explore the dataset by specifying a region of interest (ROI), which leads to the generation of a more accurate data representation inside the ROI. If even more precise accuracy is needed inside the ROI, nested ROIs are used. Experimental results show that the user can interactively explore large volume datasets such as the Visible Human male (1760x1024x1878, with a file size of 3.15 GB) on a commodity platform.Item A Lemon is not a Monstar: Visualization of Singularities of Symmetric Second Rank Tensor Fields in the Plane(The Eurographics Association, 2008) Liu, J.; Hewitt, W. T.; Lionheart, W. R. B.; Montaldi, J.; Turner, M.; Ik Soo Lim and Wen TangIn the visualization of the topology of second rank symmetric tensor fields in the plane one can extract some key points (degenerate points), and curves (separatrices) that characterize the qualitative behaviour of the whole tensor field. This can provide a global structure of the whole tensor field, and effectively reduce the complexity of the original data. To construct this global structure it is important to classify those degenerate points accurately. However, in existing visualization techniques, a degenerate point is only classified into two types: trisector and wedge types. In this work, we will apply the theory from the analysis of binary differential equations and demonstrate that, topologically, a simple degenerate point should be classified into three types: star (trisector), lemon and monstar. The later two types were mistakenly regarded as a single type in the existing visualization techniques.Item Light Field Rendering for Games(The Eurographics Association, 2008) Todt, S.; Rezk-Salama, C.; Kolb, A.; Ik Soo Lim and Wen TangThis paper studies the problem of integrating high-quality light field rendering into state-of-the-art real-time computer games. We present a complete production pipeline for generation of light fields from arbitrary complex 3D content using commercial 3D modeling software commonly used in the gaming industry. We show how recent advances in light field rendering techniques can be used to composite light fields with dynamic scene content. The results demonstrate the potential of light fields as a valuable extension to polygonal rendering techniques by employing accurate silhouette reconstruction and correct per-pixel depth values for scene composition. Level of detail techniques are applied to light fields to optimize rendering performance. Dynamic light field rendering is implemented to account for animation, deformation and varying lighting conditions.Item Localised Topology Correction for Hypertextured Terrains(The Eurographics Association, 2008) Gamito, Manuel N.; Maddock, Steve C.; Ik Soo Lim and Wen TangTerrains for computer graphics have traditionally been modelled with height fields. In the case of procedurally defined terrains, the height field is generated by a displacement map zItem Modes of Virtual Environments Integrated within Collaborative Environments(The Eurographics Association, 2008) McDerby, M. J.; Turner, M. J.; Leaver, G. W.; Ik Soo Lim and Wen TangThis paper describes the timeline of large display virtual environments used by Manchester Visualization Centre and a few of the main applications of such systems. Moreover, it describes a few simple common modes of use as well as stages of development, categorising and explaining how best practice may be achieved. In addition this paper considers the development and use in the last few years of multi-functioning spaces that combine both a large scale VE with the next generation of video conferencing system. These have been used to create new modes of interaction and collaboration.Item A New Method for Interacting with Multi-Window Applications on Large, High Resolution Displays(The Eurographics Association, 2008) Rooney, Chris; Ruddle, Roy A.; Ik Soo Lim and Wen TangPhysically large display walls can now be constructed using off-the-shelf computer hardware. The high resolution of these displays (e.g., 50 million pixels) means that a large quantity of data can be presented to users, so the displays are well suited to visualization applications. However, current methods of interacting with display walls are somewhat time consuming. We have analyzed how users solve real visualization problems using three desktop applications (XmdvTool, Iris Explorer and Arc View), and used a new taxonomy to classify users' actions and illustrate the deficiencies of current display wall interaction methods. Following this we designed a novel method for interacting with display walls, which aims to let users interact as quickly as when a visualization application is used on a desktop system. Informal feedback gathered from our working prototype shows that interaction is both fast and fluid.Item A Physical Model for the Polarized Scattering of Light(The Eurographics Association, 2008) Brayford, David; Turner, Martin; Hewitt, W. T.; Ik Soo Lim and Wen TangThe change in polarization state due to the interaction of light with the surface and beneath the surface of an object has become increasingly important in realistic image synthesis of materials such as metallic, iridescent and pearlescent paint, skin, hair and cosmetics. This paper presents a model for the anisotropic scattering of polarized light based upon the physics of light; which is capable of calculating both partial and complete polarization using a combination of Jones and Mueller calculus, as well as incorporating self shadowing effects.Item Segmenting the External Surface of a Human Skull in MR Data(The Eurographics Association, 2008) Salas, M.; Maddock, S.; Ik Soo Lim and Wen TangA method is presented to extract the outline of the skull region in coronal Magnetic Resonance (MR) images from the Visible Human Project. The starting point is the formulation of a Gradient Vector Flow (GVF) snake extended to include statistical shape information. This method exploits the diffusion process used by the GVF snake and improves its capacity to deal with occlusion problems by adding a shape term to the traditional scheme. The results of the segmentation of the MR data are compared with the results of the segmentation of CT scans of the same individual. For the MR data, the addition of a shape term improves on the results obtained by using a GVF snake alone.