EG UK Theory and Practice of Computer Graphics 2006
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Item ATIP: A Tool for 3D Navigation inside a Single Image with Automatic Camera Calibration(The Eurographics Association, 2006) Boulanger, Kevin; Bouatouch, Kadi; Pattanaik, Sumanta; Louise M. Lever and Mary McDerbyAutomatic Tour Into the Picture (ATIP) is an extension of the Tour Into the Picture method [HAA97] that allows an approximative but visually convincing 3D walk-through inside a single image by rendering a box textured using the input image data. The original algorithm requires a long and tedious user interaction to determine the box dimensions and the perspective parameters, and imposes several constraints on the input image orientation. The goal of this paper is to present a framework providing fully automatic and fast camera calibration for any view orientation without using a calibration target. Our method reduces the user interaction, hence only a couple of seconds are required between the input image loading and the final walk-through.Item Augmented Reality with Multilayer Occlusion(The Eurographics Association, 2006) Feng, Yan; Chen, Yimin; Louise M. Lever and Mary McDerbyAn algorithm for realizing multilayer occlusion in augmented reality (AR) is presented in this paper. We have designed a special scene graph tree comprised of some special nodes, namely EMO nodes. According to the location of real moving object, different EMO node will be activated in real-time, consequently realizing the multilayer occlusion. Differing qualitatively from previous work in AR occlusion, our algorithm realizes multilayer occlusion, and its application domain involves indoor-field occluded objects, which are several meters distant from the viewer. Previous related work has focused on monolayer occlusion, and near-field occluded objects, which are within or just beyond arm s reach. In addition, BP neural network is improved to correct the nonlinear error of magnetic sensor, consequently to detect occlusion more effectively. Experimental results are provided to demonstrate the multilayer indoor-field occlusion.Item Automatic Stroke Extraction and Stroke Ordering Based on TrueType Font(The Eurographics Association, 2006) Koo, Sang Ok; Jang, Hyun Gyu; Won, Kwang Hee; Jung, Soon Ki; Louise M. Lever and Mary McDerbyIn this paper, we suggest a method that extracts strokes of Chinese characters and orders them automatically based on glyph data from TrueType Font. TrueType Font contains glyph of characters whose format is a series of bézier curves and they are arranged according to a rule. Using clues, we extract the vectors which consist of each stoke and reconstruct each stroke to the format similar to a TrueType Font. In addition, we label every stroke and define the orders of strokes using stroke labels and indicate the relations among them. Because all of the processes are performed automatically, we can minimize the time and the effort to make stroke database of Chinese characters. Moreover, because the final data has vector graphics format, it can be applied to the study of graphical contents using glyphs as well as to simple font generation for the Chinese education.Item Collision Detection for Deformable Objects using Octrees(The Eurographics Association, 2006) Madera, F. A.; Day, A. M.; Laycock, S. D.; Louise M. Lever and Mary McDerbyWe present an algorithm for collision detection between multiple deformable objects translating in a large environment. We use Spatial Partitioning to subdivide the scene and a Bounding Volume Hierarchy to decompose the objects, using octrees in both cases. The algorithm is divided in two parts, the Broad and Narrow Phases, with objects that can be rigid or deformable. In the Broad Phase, an octree is used to partition the scene and cull away the object s Bounding Volumes that are distant. In the Narrow Phase, a hierarchical decomposition of Axis Aligned Bounding Boxes or spheres is employed to reduce the number of primitives in the pairwise comparisons. In summary this work is a general-purpose collision detection technique for performing real time collision detection of deformable bodies in interactive 3D applications.Item Computing Static Electricity on Human Hair(The Eurographics Association, 2006) Sobottka, Gerrit; Weber, Andreas; Louise M. Lever and Mary McDerbyWe present a framework to study electrical charge phenomena on human hair. We propose a fiber based hair model which bases on the special theory of Cosserat Rods to overcome the well known difficulties one has to deal with when simple particle systems are used. We show how such models can efficiently be employed in conjunction with the fast multipole method to account for Coulomb far-field interactions. Furthermore, we extend our model such that we can account for environmental conditions.Item Curvature-Based Segmentation for Sketch Understanding(The Eurographics Association, 2006) Zheng, Wentao; Liu, Zhiyu; Sun, Zhengxing; Louise M. Lever and Mary McDerbySegmentation is known as an important and fundamental task in sketch understanding, by which free hand drawing is processed into primitive geometric units such as line segments, arcs, etc. Usually, two types of information are used in segmentation: drawing speed and curvature. This paper first analyzes the necessity of drawing speed and curvature, then concludes that curvature is better for segmentation, and drawing speed is harmful to later steps in sketch understanding. To provide a fast and robust method for segmentation, we device a window-controlled relative curvature calculation method which is immune to ink noise. Based on the method, our segmentation approach adopts a two-step strategy which shows satisfying experimental results.Item Evolving Body Kinematics for Virtual Characters(The Eurographics Association, 2006) Gatzoulis, C.; Tang, W.; Stoddart, W. J.; Louise M. Lever and Mary McDerbyPhysically-based character animation systems often require complex knowledge of the underlying equations of motion. Hence, producing physically-realistic animations can be time consuming with these systems. In this paper, we present an approach that automatically searches for kinematics solutions for virtual characters. Characters learn their locomotion by evolving body kinematics. We designed two different control architectures for the character s learning process with predefined motion data sets and a feedback system. The first system is based on a layer of genetic algorithms (GA) and the second is based on a Reinforcement Learning (RL) approach. Animation systems based on these control architectures require little knowledge of the physics equations of motions, but can generate physically-feasible motions in real-time through observations of available motion data sets, such as previous animations or motion capture data. This animation approach allows animators to construct easily realistic body kinematics motion for computer game characters. Embedded with simulated musculature of human body, the system also has applications in sports and physiotherapy for motion visualization. The test data also demonstrates the advantages and drawbacks of the two types of control methods.Item Expressive and Dynamic Deformation of Animated Computer-Generated Characters(The Eurographics Association, 2006) Noble, Paul; Tang, Wen; Louise M. Lever and Mary McDerby3D computer animated characters often lack the communicative power and the expressiveness of traditional animation, especially when used in non-photorealistic graphical representations. Inspired by a talk by Pixar Animation Studios at Animex 2005 [WR05] and based upon the animation and cartooning concepts of lines of action and motion, we present an expressive animation tool that emphasizes and accentuates the intentions of the animator derived from the skeleton-driven animation. Motion and pose-based shape deformations are automatically generated to quickly add an emotive layer to an animated character. This warping of the character geometry also provides a novel solution to the problem of implied motion in non-photorealistic still images.Item Fast Rendering of Complex Dynamic Scenes(The Eurographics Association, 2006) Kovalcík, Vit; Sochor, Jiri; Louise M. Lever and Mary McDerbyWe present a novel algorithm capable of rendering complex dynamic scenes at high frame rates. The key part of the algorithm is occlusion culling which is performed by an optimized usage of the hardware occlusion queries. The spatial organization of the scene using 2-level BSP-like hierarchy helps to speed up evaluating full and partial occlusion of the objects. The algorithm handles both static and dynamic objects and places no restrictions on the shape of objects.Item Flexible Interaction with Large Point-Based Datasets(The Eurographics Association, 2006) Rosiuta, A.; Reina, G.; Ertl, T.; Louise M. Lever and Mary McDerbyWe present an application for interacting with large, point-based datasets built with commodity off-the-shelf hardware. Our system works on ordinary workstations with mouse and keyboard interaction as well as on immersive multi-head VR systems with tracked input devices. This approach allows thermodynamics and astrophysics researchers to interactively navigate, filter and inspect large datasets that result from particle-based simulations as used in those areas. We make use of an adaptive, hierarchical rendering approach and extend its data structures to optimize the interaction performance to be usable with datasets of hundreds of thousands of particles. We prove the validity of our concepts with informal user studies both in the application area and the computer science context.Item GraSSML: Smart Schematic Diagrams, XML and Accessibility(The Eurographics Association, 2006) Fredj, Z. Ben; Duce, D. A.; Louise M. Lever and Mary McDerbyThis paper describes work in progress at Oxford Brookes University. The project called Graphical Structure Semantic Markup Languages (GraSSML) aims at defining higher-level diagram description languages for the World Wide Web, which capture the structure and the semantics of a diagram and enable the generation of accessible and "smart" presentations in different modalities such as speech, text, and graphics. GraSSML is broken down into three levels: semantics, structure and presentation. Each of these levels captures a specific aspect of a diagram. The semantic level language is highly dependent on the type of diagram considered and the knowledge of the domain (ontology) in which it is used. Using the proposed approach, the structure and the semantics of the diagram is made available at the creation stage. The availability of this information offers new possibilities allowing Web Graphics to become "smart". The paper outlines the relevant limitations of SVG and some approaches aiming to resolve the problem of graphic accessibility. It then describes our approach in addressing some of these limitations and presents the new possibilities that these smart graphics lead to.Item Hand Motion Capture and Tracking in 3D Animation(The Eurographics Association, 2006) Condell, J.; Moore, G.; Moore, J.; Louise M. Lever and Mary McDerbyThis extended abstract details previous methods for motion tracking and capture in 3D animation and in particular that of hand motion tracking and capture. Our research aims to enable gesture capture with interpretation of the captured gestures and control of the target 3D animation software. This stage of the project involves the development and testing of a motion analysis system. A motion analysis system is being built from algorithms recently developed. We review current software and research methods available in this area and describe our work-in-progress. Motion capture is a technique of digitally recording the movements of real entities, usually humans. It was originally developed as an analysis tool in biomechanics research, but has grown increasingly important as a source of motion data for computer animation. In this context it has been widely used for both cinema and video games. Hand motion capture and tracking in particular has received a lot of attention because of its critical role in the design of new Human Computer Interaction methods and gesture analysis. One of the main difficulties is the capture of human hand motion.Item HyperStreamball Visualization for Symmetric Second Order Tensor Fields(The Eurographics Association, 2006) Liu, J.; Turner, M.; Hewitt, W. T.; Perrin, J. S.; Louise M. Lever and Mary McDerbyThis paper proposes a new 3D tensor glyph called a hyperstreamball that extends streamball visualization used within fluid flow fields to applications within second order tensor fields. The hyperstreamball is a hybrid of the ellipsoid, hyperstreamline and hyperstreamsurface. With the proposed system a user can easily interactively change the visualization. First, we define the distance of the influence function which contributes a potential field that can be designed to highlight the three eigenvectors and eigenvalues of a real symmetric tensor at any sample point. Second, we discuss the choice of source position and how the user can control the parameter mapping between the field data and the implicit function. Finally, we test our results using both synthetic and real data that shows the hyperstreamball's two main advantages: one is that hyperstreamballs blend and split with each other automatically depending on the tensor data, and the other advantage is that the user can achieve both discrete and continuous representation of the data based on a single geometrical description.Item An Interactive Multiscale Framework for Enhancement and Visualization of 2D and 3D Image Data(The Eurographics Association, 2006) Graham, Andrew D.; Turner, Martin J.; Hewitt, Terry; Louise M. Lever and Mary McDerbyWe present an interactive, multiscale framework for enhancement and de-noising of images and volumes for the purposes of medical image visualization. Among the visualization issues addressed are noise suppression and contrast enhancement. Previous research in this area has concentrated on non-linear operations performed either on the images or their decomposed wavelet coefficients. The vast majority of this research uses global operations over the whole image and sets standard operation parameters for all images. We describe novel non-linear operators and visualization methods that allow the operation parameters to be tailored to an unfamiliar image by the viewer, thereby increasing the adaptability and effectiveness of the enhancement process.Item A Mixed Reality Anatomy Teaching Tool(The Eurographics Association, 2006) Thomas, Rhys G.; John, Nigel W.; Lim, Ik Soo; Louise M. Lever and Mary McDerbyIn this paper we present an inexpensive Mixed Reality software tool for training medical students in anatomy. The software integrates the ARToolkit and Visualization Toolkit (VTK) to create a novel interactive environment in which the user can manipulate the position and orientation of the volume rendering using a plastic model of the organ to be observed. The volume rendering can then be clipped relative to an arbitrary plane to reveal data from its interior, using a second prop.Item Out of core Polyhedral Union and its Application to Interactive Shadow Rendering(The Eurographics Association, 2006) Fedorkiw, J.; Smith, C.; Ghali, S.; Louise M. Lever and Mary McDerbyFour methods for storing a set of points using a computer are currently known: Boundary representations, Constructive Solid Geometry, Binary Space Partitioning trees, and Nef polyhedra. We describe a time and spaceefficient BSP-based algorithm for computing the union of a set of solids and compare it with the other solid representations. The algorithm does not require that the entire tree fit in memory; it only needs to maintain the path from the root to one node in the tree at a time. We show that the algorithm is practical by providing time and space statistics. We also show the benefit of using the resulting union solid for computing interactive shadows.Item Perceived Rendering Thresholds for High-Fidelity Graphics on Small Screen Devices(The Eurographics Association, 2006) Aranha, M.; Debattista, K.; Chalmers, A.; Hill, S.; Louise M. Lever and Mary McDerbySmall screen devices, also known as small-form-factor (SFF) devices including mobile phones and ultra mobile PCs are increasingly ubiquitous. Their uses includes gaming, navigation and interactive visualisation. SFF devices are, however, inherently limited by their physical characteristics for perception as well as limited processing and battery power. High-fidelity graphic systems have significant computational requirements which can be reduced through use of perceptually-based rendering techniques. In order to exploit these techniques on SFF devices a sound understanding of the perceptual characteristics of the display device is needed. This paper investigates the perceived rendering threshold specific for SFF devices in comparison to traditional display devices. We show that the threshold for SFF systems differs significantly from typical displays indicating substantial savings in rendering quality and thus computational resources can be achieved for SFF devices.Item Perception-based Lighting Design(The Eurographics Association, 2006) Ha, Hai Nam; Olivier, Patrick; Louise M. Lever and Mary McDerbyPerception-based lighting design approaches model image quality using a cognitively grounded objective function which is in turn optimised through manipulation of the lighting parameters of a scene. We present, and demonstrate, a detailed implementation of perception-based lighting design, including the application and evaluation of stochastic optimisation using genetic algorithms.Item Physically Based Simulation and Visualization of Fire in Real-Time using the GPU(The Eurographics Association, 2006) Rødal, Samuel; Storli, Geir; Gundersen, Odd Erik; Louise M. Lever and Mary McDerbyIn this paper we present a physically based framework for real-time simulation and visualization of fire using the GPU. The physics of fire is modeled through a combination of a fluid solver and a combustion process causing the characteristic motion of fire. The simulation results are then rendered using a particle system combined with a black-body radiation model where the physically based simulation governs both the motion and appearance of the particles. By performing individual slice simulations in 2D and combining them using volumetric extrusion we achieve better performance than by performing the simulation in 3D without compromising the visual quality. Thus, achieving our goal of visualizing bonfire and torch-like fire effects with high visual quality in real-time.Item Polynomial Approximation of Blinn-Phong Model(The Eurographics Association, 2006) Öztürk, Aydin; Bilgili, Ahmet; Kurt, Murat; Louise M. Lever and Mary McDerbyThe Phong model has been one of the oldest and the most popular reflection models in Computer Graphics. It can be used to model specular highlights of various materials. In this paper, we consider a polynomial model and obtain a linear approximation of the Blinn-Phong model. Approximation errors were obtained for the proposed model and empirical comparisons were made using a measured BRDF data set. Based on the empirical results, it is shown that proposed model provides visually convincing representation of BRDF and performs well for modeling the surface reflectance.