2009 - EG UK Theory and Practice of Computer Graphics

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https://diglib.eg.org/handle/10.2312/904

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Fast and Accurate Finite Element Method for Deformation Animations
(The Eurographics Association, 2009) Tang, Wen; Wan, Tao Ruan; Niquin, Ceddric; Schildknecht, Alexandre; Wen Tang and John Collomosse
We present a matrix clustering method for speeding up finite element computations for non-rigid object animation. The method increases the efficiency of computing deformation dynamics through a compression scheme that decomposes the large force-displacement matrix into clusters of smaller matrices in order to facilitate the run-time computations of linear finite element based deformations. The deformation results are compared with the results produced by using modal analysis method and the standard linear finite element algorithm. We demonstrate that the proposed method is stable with comparative computational speed to modal analysis method. A hierarchical skeleton-based system is also implemented to add constraints to material nodes. Thus, real-time deformations can be directed by motion captured data sets or key-framed animations.
Towards Object Recognition using HDR Video, Stereoscopic Depth Information and SIFT
(The Eurographics Association, 2009) May, Michael; Morris, Tim; Markham, Keith; Crowther, William J.; Turner, Martin J.; Wen Tang and John Collomosse
In this paper we propose a framework that will recognise objects from a moving platform using scale invariant features, high dynamic range (HDR) video and stereoscopic depth information. The paper focuses on initial work involving feature extraction from HDR images using SIFT. Initial results show an increase in the number of features extracted from HDR images compared to conventional, low dynamic range (LDR), images.
Automatically Generating Virtual Humans using Evolutionary Algorithms
(The Eurographics Association, 2009) Albin-Clark, Adrian; Howard, Toby; Wen Tang and John Collomosse
Abstract Virtual Humans are used in many applications either as an embodiment of a real person (an "avatar"), or under the control of a computer program (an "agent" or "non-player character"). The automatic generation of Virtual Humans is a challenging problem if they are to look both plausible and unique within a population. We present an approach which exploits the power of Evolutionary Algorithms (EAs), and provide illustrative examples of how our methods may be realised within the context of surface-based model geometry.
Real-time Rendering of Deformable Translucent Objects
(The Eurographics Association, 2009) Benmounah, Nadir; Jolivet, Vincent; Ghazanfarpour, Djamchid; Wen Tang and John Collomosse
This paper introduces an efficient real-time shading model to simulate light transport in translucent materials. In this work no pre-processing step is needed, allowing us to deform translucent objects at interactive rates. The proposed technique avoids the pre-processing of texture atlas and texture coordinates that may entail distortions and self-occlusion errors. We create a cube map texture atlas on the GPU by a specific projection providing accurate access to neighborhood information is accurate. The texture atlas is generated on-the-fly each time the mesh geometry is modified, allowing us to deform the object geometry in real time keeping valid the subsurface light transport computation.
Influencing User Attention Using Real-Time Stylised Rendering
(The Eurographics Association, 2009) Redmond, Niall; Dingliana, John; Wen Tang and John Collomosse
In this paper, we present a series of experiments that were conducted to further understand how using adaptive levels of artistic abstraction within an interactive 3D scene can influence user gaze behaviour. We found that when an object was placed in the center of stylised focus, users took significantly less time to complete a search and recognition task in comparison to normal renderings or when the target object was heavily abstracted i.e. stylistically out-of-focus. We also compared a number of different abstraction techniques and found that some abstraction styles consistently lead to faster search times than others. Finally we performed experiments using an eye-tracker to show that our real-time abstraction techniques can successfully draw user attention to specific objects within an interactive scene. We believe that our experimental framework will be useful in the future for comparing the effectiveness of different non-photorealistic styles in influencing a user's perception of a scene.
An Adaptive Sampling Approach to Incompressible Particle-Based Fluid
(The Eurographics Association, 2009) Hong, Woosuck; House, Donald H.; Keyser, John; Wen Tang and John Collomosse
We describe an adaptive particle-based technique for simulating incompressible fluid that uses an octree structure to compute inter-particle interactions and to compute the pressure field. Our method extends the hybrid Flip technique by supporting adaptive splitting and merging of fluid particles, and adaptive spatial sampling for the reconstruction of the velocity and pressure fields. Particle splitting allows a detailed sampling of fluid momentum in regions of complex flow. Particle merging, in regions of smooth flow, reduces memory and computational overhead. The octree supporting field-based calculations is adapted to provide a fine spatial reconstruction where particles are small and a coarse reconstruction where particles are large. This scheme places computational resources where they are most needed, to handle both flow and surface complexity. Thus, incompressibility can be enforced even in very small, but highly turbulent areas. Simultaneously, the level of detail is very high in these areas, allowing the direct support of tiny splashes and small-scale surface tension effects. This produces a finely detailed and realistic representation of surface motion.
Hardware Accelerated Shaders Using FPGAs
(The Eurographics Association, 2009) Goddard, Luke; Stephenson, Ian; Wen Tang and John Collomosse
We demonstrate that Field Programable Gate Arrays (FPGAs) can be used to accelerate shading of surfaces for production quality rendering (a task standard interactive graphics hardware is generally ill-suited to) by allowing circuits to be dynamically created at run-time on standard commercial logic boards. By compiling shaders to hardware descriptions, they can be executed on FPGA with the performance of hardware without sacrificing the flexibility of software implementations. The resulting circuits are fully pipelined, and for circuits within the capacity of the FPGA can shade MicroPolygons at a fixed rate independent of shader complexity.
Visual Representation of Multiple Associations in Data using Constrained Graph Layout
(The Eurographics Association, 2009) Xu, Weijia; Sreevalsan-Nair, Jaya; Wen Tang and John Collomosse
This paper presents a new approach for simultaneously visualizing multiple exclusive associations, defined on the same dataset, using constrained graph layout. We work with two different associations at a time, which can be represented as a binary graph operation. Given an initial graph layout which represents an association of the data, another set of constraints is applied to the graph to represent a second association on the same dataset to obtain the final layout. Our motivation is to preserve some features of the first layout as well as to achieve a simultaneous view of both the associations. We use this approach generically for three applications: for visualization of data with geometric and categorical constraints, respectively. We further propose to extend it to multiple associations, by using the binary operation multiple times.
A Framework for Physically Based Forest Fire Animation
(The Eurographics Association, 2009) Gundersen, Odd Erik; Skjermo, Jo; Wen Tang and John Collomosse
Abstract In this paper, we propose a conceptual framework for animating physically based forest fires. Animating forest fire is a computationally demanding task as trees are intricate structures and fire is a highly complex process. The framework is divided into three conceptual levels, which are a large scale forest fire simulation, a small scale tree fire simulation, and an intermediate level connecting the two. Problems with and possible solutions to all three levels are discussed. Based on this discussion, a complete framework is proposed.
Aesthetic-Interaction: Exploring the Importance of the Visual Aesthetic in the Creation of Engaging Photorealistic VR Environments
(The Eurographics Association, 2009) Carroll, Fiona; Wen Tang and John Collomosse
Nearly forty years since its conception, the medium of VR is still an enigma. In many ways, it is a medium that still lacks its own uniform language. VR, and particularly photorealistic VR, is a medium that is so occupied in developing its technological capabilities that its other hidden strengths have been neglected. The research presented in this paper is therefore interested in building a more holistic understanding of the "language" of VR, and aims to look beyond the technological in order to explore the creative and experiential side of VR. The goal of the paper is to cross fertilise the fields of HCI, photorealistic virtual reality and visual aesthetics. In it, the author focuses on the design of an aesthetic-interaction and in doing so, implements a comparative study to explore how the strategic patterning of the aesthetic elements (particularly colour) within the photorealistic VR environment can ensure a more engaging VR experience. In conclusion, the author claims that the next generation design of photorealistic VR experiences should consider a balanced combination of both science and art. It highlights that aesthetics can play as important a role as the development of new and more efficient technologies in getting to the heart of the "engaging" photorealistic VR experience.
Interactive Relighting for Stage Use
(The Eurographics Association, 2009) Stephenson, Ian; Wen Tang and John Collomosse
Re-lighting by combining images taken under known lighting conditions to synthesise new lighting configurations is a simple, but powerful technique capable of producing impressive results. However it has found little practical application. Here we demonstrate the integration of a relighting tool into a typical theatrical lighting system, to provide real time previews both offline when the stage is unavailable, and during performance.
Touching The Invisible - Molecular Haptics
(The Eurographics Association, 2009) Davies, R. Andrew; Maskery, James S.; John, Nigel W.; Wen Tang and John Collomosse
Novel, simple, cost-effective applications combining haptics and computer graphics for the study of key chemical concepts such as reactivity and periodicity at AS/A-level and undergraduate level are described.
An Improved Precise Multi-contact Haptic Visualization
(The Eurographics Association, 2009) Flasar, Jan; Kovalcík, Vít; Sochor, Jirí; Wen Tang and John Collomosse
We present an improved multi-contact haptic visualization method based on the Spatialized Normal Cone Hier- archies (SNCH). Though this approach is not entirely new, we have implemented several improvements in order to significantly increase precision and robustness over the previous method. As a consequence we are able to simulate much harder surfaces and give users the chance to feel smaller features on the surface compared to the original approach. This was achieved mostly by using more precise triangle to triangle distance calculations and a different triangle visibility algorithm. As these computations are expensive, we have also developed a new technique to reduce the number of calculations required. Currently, our algorithm is capable of visualizing haptic interactions between two 3D models consisting of tens of thousands of triangles. The simulation is performed in real-time and is seamlessly integrated into a virtual-reality component-based system named VRECKO.
A Haptic System for Drilling into Volume Data with Polygonal Tools
(The Eurographics Association, 2009) Liu, Yu; Laycock, Stephen D.; Wen Tang and John Collomosse
With the developments of volume visualization 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. This paper presents a haptic system for using arbitrary polygonal tools for drilling into volume data. By using this system, users can select from a variety of virtual tools to gain continuous and smooth force feedback during the drilling of volumetric data. As the user manipulates the haptic device the tool typically only moves a small amount. By considering the locations of the data points, that are modified when drilling, a relatively small number of voxels are determined each frame which must be recomputed by a Marching Cubes algorithm.
Diffusion and Fractional Diffusion Based Image Processing
(The Eurographics Association, 2009) Blackledge, Jonathan Michael; Wen Tang and John Collomosse
We consider the background to describing strong scattering in terms of diffusive processes based on the diffusion equation. Intermediate strength scattering is then considered in terms of a fractional diffusion equation which is studied using results from fractional calculus. This approach is justified in terms of the generalization of a random walk model with no statistical bias in the phase to a random walk that has a phase bias and is thus, only 'partially' or 'fractionally' diffusive. A Green's function solution to the fractional diffusion equation is studied and a result derived that provides a model for an incoherent image generated by light scattering from a tenuous random medium. Applications include image enhancement of star fields and other cosmological bodies imaged through interstellar dust clouds. An example of this application is given.
Discrete Element Modelling Using a Parallelised Physics Engine
(The Eurographics Association, 2009) Longshaw, Stephen M.; Turner, Martin J.; Finch, Emma; Gawthorpe, Robert; Wen Tang and John Collomosse
Discrete Element Modelling (DEM) is a technique used widely throughout science and engineering. It offers a convenient method with which to numerically simulate a system prone to developing discontinuities within its structure. Often the technique gets overlooked as designing and implementing a model on a scale large enough to be worthwhile can be both time consuming and require specialist programming skills. Currently there are a few notable efforts to produce homogenised software to allow researchers to quickly design and run DEMs with in excess of 1 million elements. However, these applications, while open source, are still complex in nature and require significant input from their original publishers in order for them to include new features as a researcher needs them. Recently software libraries notably from the computer gaming and graphics industries, known as physics engines, have emerged. These are designed specifically to calculate the physical movement and interaction of a system of independent rigid bodies. They provide conceptual equivalents of real world constructions with which an approximation of a realistic scenario can be quickly built. This paper presents a method to utilise the most notable of these engines, NVIDIAs PhysX, to produce a parallelised geological DEM capable of supporting in excess of a million elements.
Calibrating a COTS Monitor to DICOM Standard
(The Eurographics Association, 2009) Grimstead, Ian J.; Avis, Nick J.; Wen Tang and John Collomosse
Abstract We present a method for calibrating a commodity, off-the-shelf (COTS) monitor (costing in the region of £200) to produce a greyscale image approximately calibrated to the DICOM standard, rather than require a 10-bit radiology monitor (costing in the region of £10,000). We use the concept of PseudoGrey to extend the available shades of grey from 256 to 5,800, which is in excess of a 12-bit greyscale. The chromaticity of the resulting greyscale is analysed to verify that the colour introduced does not unduly detract from a pure greyscale image. The behaviour of low intensity levels in the COTS monitor is also analysed, showing that a naive approach to estimating luminance from individual passes through the red, green and blue components is insufficient to produce an accurate intensity range. The results show that we can achieve a basic DICOM calibration (with FIT and LUM tests), but we have yet to test for further variability (such as off-axis deterioration in brightness or inconsistent luminance across a display). As well as displaying medical images, this approach may be of use in other areas requiring a high dynamic range, such as thermal imagery or images taken through multiple alternative exposures.
Simulation of X-ray Attenuation on the GPU
(The Eurographics Association, 2009) Vidal, Franck; Garnier, Manuel; Freud, Nicolas; Létang, Jean Michel; John, Nigel W.; Wen Tang and John Collomosse
In this paper, we propose to take advantage of computer graphics hardware to achieve an accelerated simulation of X-ray transmission imaging, and we compare results with a fast and robust software-only implementation. The running times of the GPU and CPU implementations are compared in different test cases. The results show that the GPU implementation with full floating point precision is faster by a factor of about 60 to 65 than the CPU implementation, without any significant loss of accuracy. The increase in performance achieved with GPU calculations opens up new perspectives. Notably, it paves the way for physically-realistic simulation of X-ray imaging in interactive time.
Object Interaction Using Tabulated Spheres Subsets
(The Eurographics Association, 2009) Newball, Andres A. Navarro; Wyvill, Geoff; McCane, Brendan; Wen Tang and John Collomosse
Tabulated Sphere Subsets (TSSs) provide a fast way to approximate collision tests between objects whose motion is constrained. A TSS is a subset of a set of spheres that approximate the shape of two objects that might collide. The subset represents only those spheres that can collide under the constrained motion. A TSS is created in three steps: 1) approximating the mesh with spheres; 2) searching the space of possible motion to find which spheres may collide: 3) extracting the spheres required for collision tests and building the table. We applied TSSs to jaw motion and skin/muscle interaction in a model dog and measured the number of spheres generated and the number of calculations needed for collision tests. In these cases TSSs outperforms several standard techniques.
Markerless Visual Human Movement Tracking for HCI: What Frequency?
(The Eurographics Association, 2009) Kahlesz, Ferenc; Klein, Reinhard; Wen Tang and John Collomosse
This paper tries to establish a minimal tracking frequency limit for visual human movement tracking algorithms that intend to be useful for the realization of some kind Human-Computer-Interaction (HCI) metaphor. More specifically, we examine the question of this minimal frequency for Augmented/Virtual Reality (AR/VR) navigation and 3D object manipulation. We approach the question from three different perspectives: shortly reviewing non-visual and visual marker-based solutions integrated regularly into AR/VR systems, spectral analysis of human movement and latency implications for AR/VR settings. Finally, we conclude the paper by combining and discussing the results from these different areas. We find that tracking with update rates as low as 12.5Hz can provide a usable basis for interaction. The most important message of the paper is that stable and working (even if slow, when compared to other techniques) markerless tracking algorithms are desperately needed because only working online with and based on such systems can the pros and cons of markerless tracking be evaluated.

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