EG UK Theory and Practice of Computer Graphics 2010

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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.
Agent-based Large Scale Simulation of Pedestrians With Adaptive Realistic Navigation Vector Fields
(The Eurographics Association, 2010) Karmakham, Twin; Richmond, Paul; Romano, Daniela M.; John Collomosse and Ian Grimstead
A large scale pedestrian simulation method, implemented with an agent based modelling paradigm, is presented within this paper. It allows rapid prototyping and real-time modifications, suitable for quick generation and testing of the viability of pedestrian movement in urban environments. The techniques described for pedestrian simulation make use of parallel processing through graphics card hardware allowing simulation scales to far exceed those of serial frameworks for agent based modelling. The simulation has been evaluated through benchmarking of the performances manipulating population size, navigation grid, and averaged simulation steps. The results demonstrate that this is a robust and scalable method for implementing pedestrian navigation behaviour. Furthermore an algorithm for generating smooth and realistic pedestrian navigation paths that works well in both small and large spaces is presented. An adaptive smoothing function has been utilised to optimise the path used by pedestrian agents to navigate around in a complex dynamic environment. Optimised and un-optimised vectors maps obtained by applying or not such function are compared, and the results show that the optimized path generates a more realistic flow.
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.
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.
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.
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.
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.
Comparison of Different Types of Visemes using a Constraint-based Coarticulation Model
(The Eurographics Association, 2010) Lazalde, Oscar M. Martinez; Maddock, Steve; John Collomosse and Ian Grimstead
A common approach to producing visual speech is to interpolate the parameters describing a sequence of mouth shapes, known as visemes, where visemes are the visual counterpart of phonemes. A single viseme typically represents a group of phonemes that are visually similar. Often these visemes are based on the static poses used in producing a phoneme. In this paper we investigate alternative representations for visemes, produced using motion-captured data, in conjunction with a constraint-based approach for visual speech production. We show that using visemes which incorporate more contextual information produces better results that using static pose visemes.
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
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 .
Craniofacial Reconstruction Based on Skull-face Models Extracted from MRI Datasets
(The Eurographics Association, 2010) Salas, Miguel; Maddock, Steve; John Collomosse and Ian Grimstead
We present a method for extracting skull and face models from MRI datasets and show how the resulting dataset is used in a craniofacial reconstruction (CFR) system. Datasets for 60 individuals are used to produce a database of 3D skull-face models, which are then used to give faces to unknown skulls. In addition to the skull-face geometry, other information about the individuals is known and can be used to aid the reconstruction process. The results of the system were evaluated using different criteria providing the system with different combinations of age, gender, body build and geometric skull features. Based on a surface to surface distance metric, the real and estimated faces produced were compared using different head models from the database with a leave-one-out strategy. The reconstruction scores obtained with our CFR system were comparable in magnitude (average distance less than 2.0 mm) to other craniofacial reconstruction systems. The results suggest that it is possible to obtain acceptable face estimations in a CFR system based on skull-face information derived from MRI data.
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.
Efficient Image Blur in Web-Based Applications
(The Eurographics Association, 2010) Kraus, Martin; John Collomosse and Ian Grimstead
Scripting languages require the use of high-level library functions to implement efficient image processing; thus, real-time image blur in web-based applications is a challenging task unless specific library functions are available for this purpose. We present a pyramid blur algorithm, which can be implemented using a subimage copy function, and evaluate its performance with various web browsers in comparison to an infinite impulse response filter. While this pyramid algorithm was first proposed for GPU-based image processing, its applicability to web-based applications indicates that some GPU techniques are of more general interest than previously assumed.
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.
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.
From Tabular Data to Metaphoric Landscape Visualisation - A Template-based Approach
(The Eurographics Association, 2010) Mohamed, Farhan; Chen, Min; Grant, Phil W.; John Collomosse and Ian Grimstead
This paper presents a template-based approach to the generation of metaphoric visualisation from tabular data. This technique allows a coherent transformation between a relatively abstract visual representation (e.g., a treemap) to a more expressive metaphor (e.g., a virtual atlas). It enables easy customisation of existing metaphors by ordinary users and uncomplicated introduction of new metaphors by expert users. It provides automation in much of the pipeline for creating a metaphoric visualisation, except aspects where crucial semantic input is necessary. The technique was realised in a software system, vis4me2. As a case study, the outcome of the latest UK Research Assessment Exercise (RAE2008) was used to demonstrate the usability and effectiveness of this technique.
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, David; 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.
An Improved Discrete Level of Detail Model Through an Incremental Representation
(The Eurographics Association, 2010) Ribelles, Jose; López, Angeles; Belmonte, Oscar; John Collomosse and Ian Grimstead
Real-time applications such as computer and video games, virtual reality and scientific simulation require rendering of complex models for realism. Graphics rendering engines include multiresolution modelling techniques to accelerate the visualization process. The Discrete Level of Detail framework (DLoD) is usually the most popular while the Continuous Level of Detail framework (CLoD) is still not as widely used by software developers. In this paper, we first discuss the benefits and drawbacks of both frameworks. Then, we present a model based on coding a discrete number of levels of detail (LoDs), with more LoDs coded than is usual in DLoD, and with an incremental representation, which is often used in CLoD. This model obtains a performance similar to DLoD by providing optimized LoDs for efficient visualization, while the popping effect is imperceptible. We present specific proposals for each of the three main stages involved in multiresolution processing: geometry simplification, construction of the incremental representation and retrieval of either uniform or view-dependent LoDs.
Integrating Haptic Interaction Into An Existing Virtual Environment Toolkit
(The Eurographics Association, 2010) Scopes, Peter; Smith, Shamus P.; John Collomosse and Ian Grimstead
There is increasing demand for haptic, or touch-based, interaction in virtual environments. Although many haptic devices come with APIs to enable the development of haptic-based applications, many do not provide the same level of graphical support available in virtual environment or game technology toolkits. This paper will discuss the integration of haptic interaction into an existing virtual environment toolkit. By creating a flexible middleware component, haptic interaction and force feedback for a haptic device can augment sensory experiences in existing virtual environments. A user study was conducted to evaluate the integration of haptics and realistic physics in an example virtual environment.

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