2010 - EG UK Theory and Practice of Computer Graphics

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An Evaluation of the use of Clustering Coefficient as a Heuristic for the Visualisation of Small World Graphs
(The Eurographics Association, 2010) McGee, Fintan; Dingliana, John; John Collomosse and Ian Grimstead
Many graphs modelling real-world systems are characterised by a high edge density and the small world properties of a low diameter and a high clustering coefficient. In the "small world" class of graphs, the connectivity of nodes follows a power-law distribution with some nodes of high degree acting as hubs. While current layout algorithms are capable of displaying two dimensional node-link visualisations of large data sets, the results for dense small world graphs can be aesthetically unpleasant and difficult to read. In order to make the graph more understandable, we suggest dividing it into clusters built around nodes of interest to the user. This paper describes a graph clustering using the average clustering coefficient as a heuristic for determining which node a vertex should be assigned to. We propose that the use of clustering coefficient as a heuristic aids in the formation of high quality clusters that consist of nodes that are conceptually related to each other. We evaluate the impact of using the clustering coefficient heuristic against other approaches. Once the clustering is performed we lay out the graph using a force directed approach for each clustering individually.
Interval Based Data Structure Optimization
(The Eurographics Association, 2010) Duffy, Brian; Carr, Hamish; John Collomosse and Ian Grimstead
Isosurface extraction is a widely exploited visualization technique for volumetric data on all manner of grid representation. The basic technique is often used to explore and measure many properties of data sets of ever increasing size. Therefore, data structures and algorithms that facilitate interactive exploration and fast processing of isosurfaces of large data sets is of paramount importance. While many optimal methods have been proposed to accelerate isosurface extraction, many of these algorithms have limitations with regards to storage costs and data quantization. In some cases these limitations preclude their practical application. We present a very simple clustering and volume compression technique based on observations in the span space and show that applying this technique to existing methods can reduce their storage cost. We show results for real data validating our technique.
Computer Graphics Education and the understanding of pixel plotting algorithms using Growth Aggregation models
(The Eurographics Association, 2010) Roberts, Jonathan; John Collomosse and Ian Grimstead
It is sometimes difficult to teach fundamental aspects of computer graphics, especially pixel plotting techniques, as some students fail to engage with the material. In this paper we describe a constructionist approach to help students learn about fundamental computer graphics techniques. By getting the students to develop code that performs a growth aggregation model, principally using Diffusion Limited Aggregation techniques, reflect upon that code and make a critical analysis of their own work in a report we hope the students will learn the material. An evaluation of two years of students' work, their results and various indicators suggest that this approach has been successful and the students engaged with the material better
Screen Space Re-Rendering for the Simulation of Concert Lighting
(The Eurographics Association, 2010) Stephenson, Ian; Scanlan, Liam; John Collomosse and Ian Grimstead
The visualisation of modern concert lighting requires complex illumination models to be calculated at interactive frame rates. Each light may have 20 or more parameters which are all changing in real time. Here we present a technique which allows static scenes with rapidly changing illumination to be re-rendered quickly in graphics hardware, with support for arbitrary geometry, complex BRDFs, shadowing and volumetric fogging. The rendering algorithm is re-factored to allow changing lighting to be applied to scenes which are otherwise fully rendered, minimising the calculation required when lights are moved.
The Effect of Discretised and Fully Converged Spatialised Sound on Directional Attention and Distraction
(The Eurographics Association, 2010) Harvey, Carlo; Walker, Steve; Bashford-Rogers, Thomas; Debattista, Kurt; Chalmers, Alan; John Collomosse and Ian Grimstead
A major challenge in Virtual Reality (VR) is to be able to provide interactive rates of realism. However this is very computationally demanding and only recently has high-fidelity rendering become close to interactive rates through a series of novel exploitations of visual perception; to render parts of the scene that are not currently being attended by the viewer at a much lower quality without the difference being perceived. This paper investigates the effect spatialised directional sounds, both discrete and converged have on the visual attention of the user with and without an auditory cue present in the scene. We verify the worth of investigating subliminal saccade shifts from directional audio impulses via a pilot study to eye track participant's free viewing a scene with an audio impulse and an acoustic identifier and also with an audio impulse and no acoustic identifier versus a control. By selecting look zones, we can identify how long users are spending attending a particular area of a scene in these scenarios. This work also investigates whether the effect prevailed, and if so to what extent, with discretised spatialised sound as opposed to a fully converged audio sample. We also present a novel technique for generating interactive discrete acoustic samples from arbitrary geometry. We show that even without an acoustic identifier in the scene, directional sound provides enough of an impulse to guide subliminal saccade shifts and affect perception in such a way that this can be used to guide selective rendering of the scenes.
Computer Modelling of Theatrical Sets
(The Eurographics Association, 2010) Stephenson, Ian; Pride, Rebecca; John Collomosse and Ian Grimstead
Here we discuss the design and implementation of a modelling tool specifically targeted for use by designers of theatrical sets. By applying domain specific knowledge and contraints to the design of the software, we demonstrate a system which can be used without signifigant training, by users with no previous computer graphics experience. We present initial end user experiences of using the tool in designing a real production of The First Arabian Night .
Remote Scientific Visualization for Large Datasets
(The Eurographics Association, 2010) Turner, Martin; Leaver, George; Perrin, James; John Collomosse and Ian Grimstead
Remote scientific visualization, where rendering services are provided by larger scale systems than are available on the desktop, are becoming increasingly important as dataset sizes increase beyond the capabilities of desktop workstations. Uptake of such services relies on access to suitable visualization applications and the ability to view the resulting visualization in a convenient form. We apply five rules from the e-Science community to meet these goals with the porting of a commercial visualization package to a large scale system and the integration of this code with the Access Grid. Example use cases from Materials Science are considered.
3D Modelling of Complex Biological Structures: The Oviduct
(The Eurographics Association, 2010) Burkitt, Mark; Romano, Daniela M.; Walker, Dawn C.; Fazeli, Alireza; John Collomosse and Ian Grimstead
A novel technique using a particle system constrained by Newtonian forces is presented for the algorithmic construction of small scale, complex 3D biological structures based on real world biological data. This allows models of structures too small to be accurately recreated using medical imaging technologies such as Magnetic Resonance Imaging (MRI) to be created. The resulting model provides a geometrically realistic 3D environment which can be used to study the biological interactions which occur within. The technique is used to create a model of an oviduct, but could also be applied to similar organs such as the colon. The model is validated using measurements and visual comparisons from biological data. Finally, the technique is implemented using single-core and multi-core CPU techniques and using GPU acceleration. The performance of each implementation is then compared.
Using Processing to Develop iCove: a Tool for Interactive Coastal Oceanographic Visualization
(The Eurographics Association, 2010) George, Richard L. S. F.; Roberts, Jonathan C.; Davies, Alan G.; John Collomosse and Ian Grimstead
We have been developing iCove: the interactive coastal oceanographic visualization environment. The challenge for the ocean scientists is that their models are complex and the datasets that are generated are huge. Furthermore, the oceanographers wish to interactively investigate and quantitatively compare different runs of these models. We propose a novel visual analytics tool to permit detailed exploration through interactive data querying to enable their analysis. This paper presents our experience of building iCove in Processing especially in comparison with our previous oceanographic tool building in VTK.
Anisotropic Kuwahara Filtering with Polynomial Weighting Functions
(The Eurographics Association, 2010) Kyprianidis, Jan Eric; Semmo, Amir; Kang, Henry; Döllner, Jürgen; John Collomosse and Ian Grimstead
In this work we present new weighting functions for the anisotropic Kuwahara filter. The anisotropic Kuwahara filter is an edge-preserving filter that is especially useful for creating stylized abstractions from images or videos. It is based on a generalization of the Kuwahara filter that is adapted to the local shape of features. For the smoothing process, the anisotropic Kuwahara filter uses weighting functions that use convolution in their definition. For an efficient implementation, these weighting functions are usually sampled into a texture map. By contrast, our new weighting functions do not require convolution and can be efficiently computed directly during the filtering in real-time. We show that our approach creates output of similar quality as the original anisotropic Kuwahara filter and present an evaluation scheme to compute the new weighting functions efficiently by using rotational symmetries.
Audio-Visual Animation of Urban Space
(The Eurographics Association, 2010) Richmond, Paul; Smyrnova, Yuliya; Maddock, Steve; Kang, Jian; John Collomosse and Ian Grimstead
We present a technique for simulating accurate physically modelled acoustics within an outdoor urban environment and a tool that presents the acoustics alongside a visually rendered counterpart. Acoustic modelling is achieved by using a mixture of simulating ray-traced specular sound wave reflections and applying radiosity to simulate diffuse reflections. Sound rendering is applied to the energy response of the acoustic modelling stage and is used to produce a number of binaural samples for playback with headphones. The visual tool which has been created unites the acoustic renderings with an accurate 3D representation of the virtual environment. As part of this tool an interpolation technique has been implemented allowing a user controlled walkthrough of the simulated environment. This produces better sound localisation effects than listening from a set number of static locations.
Evaluation of A Viseme-Driven Talking Head
(The Eurographics Association, 2010) Dey, Priya; Maddock, Steve; Nicolson, Rod; John Collomosse and Ian Grimstead
This paper introduces a three-dimensional virtual head for use in speech tutoring applications. The system achieves audiovisual speech synthesis using viseme-driven animation and a coarticulation model, to automatically generate speech from text. The talking head was evaluated using a modified rhyme test for intelligibility. The audiovisual speech animation was found to give higher intelligibility of isolated words than acoustic speech alone.
Sketch-Based Posing of 3D Faces for Facial Animation
(The Eurographics Association, 2010) Gunnarsson, Orn; Maddock, Steve; John Collomosse and Ian Grimstead
This paper presents a novel approach to creating 3D facial animation using a sketch-based interface where the animation is generated by interpolating a sequence of sketched key poses. The user does not need any knowledge of the underlying mechanism used to create different expressions or facial poses, and no animation controls or parameters are directly manipulated. Instead, the user sketches the desired shape of a facial feature and the system reconstructs a 3D feature which fits the sketched stroke. This is achieved using a maximum likelihood framework where a statistical model in conjunction with Hidden Markov Models handles sketch detection, and a hierarchical statistical mapping approach reconstructs a posed 3D mesh from a low-dimensional representation.
Multiresolution Modeling Using Fractal Image Compression Techniques
(The Eurographics Association, 2010) Belmonte, Óscar; Sancho, Sergio; Ribelles, José; John Collomosse and Ian Grimstead
This work presents a new approach to the multiresolution modeling of polygonal meshes. This approach is based on the theoretically well-established fractal image compression techniques. A polygonal mesh is represented as a fractal using an iterated function system (IFS). In this way, a level of detail can be obtained over a region of the mesh by successively iterating the IFS. The main advantage is that it becomes possible to recover new levels of detail that were not present in the original mesh, so that the quality is not lost as the observer approaches the mesh. Another characteristic is that the same representation can be used over textures, and in this case the algorithm is directly implemented over the GPU. The visualization time obtained allows this new approach to be used in real-time interactive computer graphic applications.
Approximating Poisson Disk Distributions by Means of a Stochastic Dither Array
(The Eurographics Association, 2010) Alford, Jennifer R.; Sheppard, David G.; John Collomosse and Ian Grimstead
Achieving blue noise point set distributions has been a common goal of two largely separate research communities: computer graphics and digital halftoning. Computer graphics research has focused largely on geometric solutions in continuous spaces. Digital halftoning research has focused on signal processing solutions in discrete imagebased space. Usage of Poisson Disk point sets in computer graphics has grown beyond sampling, including object distribution and texturing, among others. The image-based field of digital halftoning can provide additional tools for graphics researchers and practitioners. It is of interest to explore the suitability of digital halftoning technology to two classic problems in computer graphics: (1) approximating Poisson Disk point distributions of constant density and (2) importance sampling of an underlying importance function. Exemplary methods from each field are implemented and, by applying well-established measures of the radially averaged power spectrum and anisotropy plots, are shown to be quite similar, although the approaches are mathematically not equivalent. Additionally, we compare the relative radius of the point sets. Further, the ability of dither array construction techniques to shape spectral characteristics of dot patterns is shown with several variations of design parameters.
ID-Based Rendering of Silhouettes on GPU
(The Eurographics Association, 2010) Diktas, Engin Deniz; Sahiner, Ali Vahit; John Collomosse and Ian Grimstead
When rendering object-silhouettes preprocessing is generally done primarily on the CPU. To this end primitive normals must be made consistent and the silhouette-edges need to be extracted every time the view-point is changed. In this paper we propose a pure image-based GPU-method where IDs of triangles are rendered to a texture and silhouettes are extracted based on the information stored in that texture. With this method the geometry does not need to be preprocessed or reprocessed when the view-point or the geometry is changed. Another important advantage of the proposed method over any Z-buffer based method is that it does not require any threshold value to compare against the difference between depth-values of the neighboring pixels which is difficult to adjust in perspective projection.
Implicit Surface Reconstruction and Feature Detection with a Learning Algorithm
(The Eurographics Association, 2010) Kaye, Patrizia; Ivrissimtzis, Ionnis; John Collomosse and Ian Grimstead
We propose a new algorithm for implicit surface reconstruction and feature detection. The algorithm is based on a self organising map with the connectivity of a regular 3D grid that can be trained into an implicit representation of surface data. The implemented self organising map stores not only its current state but also its recent training history which can be used for feature detection. Preliminary results show that the proposed algorithm gives good quality reconstructions and can detect various types of feature.
Anatomically Plausible Surface Alignment and Reconstruction
(The Eurographics Association, 2010) Paulsen, Rasmus R.; Larsen, Rasmus; John Collomosse and Ian Grimstead
With the increasing clinical use of 3D surface scanners, there is a need for accurate and reliable algorithms that can produce anatomically plausible surfaces. In this paper, a combined method for surface alignment and reconstruction is proposed. It is based on an implicit surface representation combined with a Markov Random Field regularisation method. Conceptually, the method maintains an implicit ideal description of the sought surface. This implicit surface is iteratively updated by realigning the input point sets and Markov Random Field regularisation. The regularisation is based on a prior energy that has earlier proved to be particularly well suited for human surface scans. The method has been tested on full cranial scans of ten test subjects and on several scans of the outer human ear.
A Multi-Windows Approach for Sketch-Based Conceptual Design System
(The Eurographics Association, 2010) Gharib, Islam; Qin, Shengfeng; John Collomosse and Ian Grimstead
Sketching plays a very important role in conceptual design. In this early stage of the design process, designers have developed some ways to help them to explore designs. Sketching is one of these methods. In this paper, a study of sketch nature was carried and a proposed sketch-based interface for modeling was designed. The sketch nature study investigated the cognitive activities in sketching process, analyzed sketches of design students and professional designers, and collected data about sketching process and sketch-based systems requirements from designers to develop sketching scenarios and determine sketch-based systems requirements. These requirements were used to design a proposed sketch-based system for conceptual design with a multi-windows approach. The proposed system aims to provide an easy way for designers to sketch freely and for ideas to flow easily by using a multi-windows approach for sketching, 3D generation and rendering.
Animating Horse Gaits and Transitions
(The Eurographics Association, 2010) Murphy, James E.; Carr, Hamish; O'Neill, Michael; John Collomosse and Ian Grimstead
Animations of horses are commonly used for entertainment purposes. A realistic animated model must move with a gait appropriate to its velocity. We present a kinematic animation system in which a horse model moves using gaits and transitions based on predictions from Dynamic Similarity theory. A Genetic Programming technique is used to evolve gait motion with dynamically adjustable limb extent. The system is controlled in real-time using a MIDI controller system based around the model's Froude number. We were successful in producing high quality animations of the horse's natural gaits and transitions.

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