EG UK Theory and Practice of Computer Graphics 2008

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https://diglib.eg.org/handle/10.2312/903

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Light Field Rendering for Games
(The Eurographics Association, 2008) Todt, S.; Rezk-Salama, C.; Kolb, A.; Ik Soo Lim and Wen Tang
This 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.
Generation and Tessellation of Tree Stems
(The Eurographics Association, 2008) Skjermo, Jo; Ik Soo Lim and Wen Tang
When 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.
Contouring with Uncertainty
(The Eurographics Association, 2008) Osorio, R. S. Allendes; Brodlie, K. W.; Ik Soo Lim and Wen Tang
The 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.
Localised Topology Correction for Hypertextured Terrains
(The Eurographics Association, 2008) Gamito, Manuel N.; Maddock, Steve C.; Ik Soo Lim and Wen Tang
Terrains 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 z
Towards Image Rendering using models of Image Manifolds
(The Eurographics Association, 2008) Woodland, A.; Labrosse, F.; Ik Soo Lim and Wen Tang
Building computer representations of real objects, which could be archaeological artifacts or planned buildings, is a very active research area. Typically objects are represented in computer memory as a collection of geometric primitives. In this paper we build on the concept of Image Manifolds, which we model in image space. This enables us to model the appearance of an object essentially as a collection of images. We discuss one possible approach to modelling image manifolds, which uses partial differential equations.
Self-Organising Maps for Implicit Surface Reconstruction
(The Eurographics Association, 2008) Yoon, Mincheol; Ivrissimtzis, Ioannis; Lee, Seungyong; Ik Soo Lim and Wen Tang
This paper proposes an implicit surface reconstruction algorithm based on Self-Organising Maps (SOMs). The SOM has the connectivity of a regular 3D grid, each node storing its signed distance from the surface. At each iteration of the basic algorithm, a new training set is created by sampling regularly along the normals of the input points. The main training iteration consists of a competitive learning step, followed by several iterations of Laplacian smoothing. After each training iteration, we use extra sample validation to test for overfitting. At the end of the training process, a triangle mesh is extracted as the zero level set of the SOM grid. Validation tests and experiments show that the algorithm can cope with the noise of raw scan data. Timing measurements and comparisons show that the algorithm is fast, because the fixed and regular connectivity of the SOM means that the search of the node nearest to a sample can be done efficiently.
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 Tang
Clutter 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.
Time-varying Image Data Visualization Framework for Application in Cardiac Catheterization Procedures
(The Eurographics Association, 2008) Ma, Ying Liang; Rhode, Kawal S.; King, Andy P.; Gao, Gang; Chinchapatnam, Phani; Schaeffter, Tobias; Razavi, Reza; Saetzler, Kurt; Ik Soo Lim and Wen Tang
Visualization plays an important role in image guided surgery. This paper presents a real-time 3D motion visualization method where pre-computed meshes of the beating heart are synchronized with and overlaid onto live X-ray images. This provides the surgeon with a navigational aid in guiding catheters during cardiac catheterization. In order to generate time-varying meshes of the beating heart, we first acquire a time-series of images of the patient using Magnetic Resonance Imaging (MRI). The MRI heart images used for the cardiac catheterization procedures can either be contrast-enhanced by injecting a contrast agent prior to imaging or they can be unenhanced. The contrast-enhanced images can easily be segmented and binarized using a fixed grey-level threshold. In this case, we can use an adaptive Delaunay-based surface extraction algorithm for mesh generation, for which specifically developed for noisy binary image data sets. For unenhanced images, we have to choose a semi-automated segmentation approach, where a region of interest in the patient's heart is outlined manually in an intermediate slice in the 3-D MRI data set and then propagated to neighbouring slices. In a next step, the extracted snake contours are propagated in time from the first phase of the cardiac cycle to subsequent phases using multiple snake contours. In this scenario, the final mesh is generated using a serial section reconstruction algorithm. However, due to the nature of the underlyling MRI images which frequently contain areas of inhomogenous contrast caused by motion and blood flow, it is difficult to generate a smooth mesh directly from the result of the previously described semi-automatic segmentation procedure. Therefore, we also introduce a contour-based mesh smoothing algorithm using a 1D Gaussian filter in order to post-process the snake contours along the series of cross-sections before reconstruction.
A Benchmarking Framework for Static Collision Detection
(The Eurographics Association, 2008) Diktas, Engin Deniz; Sahiner, Ali Vahit; Ik Soo Lim and Wen Tang
Performanceof 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.
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 Tang
The 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.
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 Tang
This 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.
Time Handling in Inverse Daylighting for CAAD
(The Eurographics Association, 2008) Tourre, Vincent; Martin, Jean-Yves; Hégron, Gérard; Ik Soo Lim and Wen Tang
This paper presents an integration of time dimension in an inverse natural lighting model. This model allows to aid the design of building openings starting from the designed volume and lighting intentions. As natural lighting evolves according to the hour of the day and the day of the year, it is necessary to take into account that the lighting intentions expressed by designers might evolve through time. The problem is to choose the way of mixing the lighting intentions or the solutions of inverse lighting simulation in order to produce useful results for designers. We propose to compute separatly individual inverse lighting at each time step in order to get an individual evaluation map, and to combine the results in a final time evaluation map. This time evaluation map allows to read easily the addition of several inverse lighting simulations, and to compute an opening shape which is intended to be used as a basis for the opening design. Our method is illustrated through test cases in order to show the inverse lighting process with time integration.
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 Tang
In 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.
A Fast Algorithm for Painterly Rendering on Mobile Devices
(The Eurographics Association, 2008) Mukundan, R.; Han, C.; Ik Soo Lim and Wen Tang
With 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.
A Haptic Rendering Algorithm for Drilling into Volume Data
(The Eurographics Association, 2008) Liu, Yu; Laycock, S. D.; Ik Soo Lim and Wen Tang
With 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.
Efficient Representation of Layered Depth Images for Real-time Volumetric Tests
(The Eurographics Association, 2008) Trapp, Matthias; Döllner, Jürgen; Ik Soo Lim and Wen Tang
Representing 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.
Grammatical Evolution for Gait Retargeting
(The Eurographics Association, 2008) Murphy, James E.; Carr, Hamish; O'Neill, Michael; Ik Soo Lim and Wen Tang
Artists 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.
GPU-based Visualisation of Protein Secondary Structure
(The Eurographics Association, 2008) Krone, Michael; Bidmon, Katrin; Ertl, Thomas; Ik Soo Lim and Wen Tang
The 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.
Space-free Shader Programming: Automatic Space Inference and Optimization for Real-time Shaders
(The Eurographics Association, 2008) Lejdfors, Calle; Ohlsson, Lennart; Ik Soo Lim and Wen Tang
The graphics processing units (GPUs) used in todays personal computers can be programmed to compute the visual appearance of three-dimensional objects in real time. Such programs are called shaders and are written in high-level domain-specific languages that can produce very efficient programs. However, to exploit this efficiency, the programmer must explicitly express space transformations necessary to implement a computation. Unfortunately, this makes programming GPUs more error prone and reduces portability of the shader programs. In this paper we show that these explicit transformations can be removed without sacrificing performance. Instead we can automatically infer the set of transformations necessary to implement the shader in the same way as an experienced programmer would. This enables shaders to be written in a cleaner, more portable, manner and to be more readily reused. Furthermore, errors resulting from incorrect transformation usage or space assumptions are eliminated. In the paper we present an inferencing algorithm as well as a prototype space-free shading language implemented as an embedded language in Python.
Image Abstraction by Structure Adaptive Filtering
(The Eurographics Association, 2008) Kyprianidis, Jan Eric; Döllner, Jürgen; Ik Soo Lim and Wen Tang
In 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.

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