EG UK Theory and Practice of Computer Graphics 2013

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https://diglib7.eg.org/handle/10.2312/908

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A Cost Effective, Accurate Virtual Camera System for Games, Media Production and Interactive Visualisation Using Game Motion Controllers
(The Eurographics Association, 2013) Bett, Matthew; Michno, Erin; McAlpine, Keneth B.; Silvester Czanner and Wen Tang
Virtual cameras and virtual production techniques are an indispensable tool in blockbuster filmmaking but due to their integration into commercial motion-capture solutions, they are currently out-of-reach to low-budget and amateur users. We examine the potential of a low budget high-accuracy solution to create a simple motion capture system using controller hardware designed for video games. With this as a basis, a functional virtual camera system was developed which has proven usable and robust for commercial testing.
Accurate and Marker-less Head Tracking Using Depth Sensors
(The Eurographics Association, 2013) Breidt, Martin; Bülthoff, Heinrich H.; Curio, Cristóbal; Silvester Czanner and Wen Tang
Parameterized, high-fidelity 3D surface models can not only be used for rendering animations in the context of Computer Graphics (CG), but have become increasingly popular for analyzing data, and thus making these accessible to CG systems in an Analysis-by-Synthesis loop. In this paper, we utilize this concept for accurate head tracking by fitting a statistical 3D model to marker-less face data acquired with a low-cost depth sensor, and demonstrate its robustness in a challenging car driving scenario. We compute 3D head position and orientation with a mesh-based 3D shape matching algorithm that is independent of person identity and sensor type, and at the same time robust to facial expressions, speech, partial occlusion and illumination changes. Different strategies for obtaining the 3D face model are evaluated, trading off computational complexity and accuracy. Ground truth data for head pose are obtained from simultaneous marker-based tracking. Average tracking errors are below 6mm for head position and below 2.5 for head orientation, demonstrating the system's potential to be used as part of a non-intrusive head tracking system for use in Augmented Reality or driver assistance systems.
Interactive Projective Texturing for Non-Photorealistic Shading of Technical 3D Models
(The Eurographics Association, 2013) Lux, Roland; Trapp, Matthias; Semmo, Amir; Döllner, Jürgen; Silvester Czanner and Wen Tang
This paper presents a novel interactive rendering technique for creating and editing shadings for man-made objects in technical 3D visualizations. In contrast to shading approaches that use intensities computed based on surface normals (e.g., Phong, Gooch, Toon shading), the presented approach uses one-dimensional gradient textures, which can be parametrized and interactively manipulated based on per-object bounding volume approximations. The fully hardware-accelerated rendering technique is based on projective texture mapping and customizable intensity transfer functions. A provided performance evaluation shows comparable results to traditional normal-based shading approaches. The work also introduce simple direct-manipulation metaphors that enables interactive user control of the gradient texture alignment and intensity transfer functions.
Resolution Estimation for Shadow Mapping
(The Eurographics Association, 2013) Ferko, Michal; Silvester Czanner and Wen Tang
We present an approach to efficiently reduce shadow map resolution while retaining high quality hard shadows. In the first step, we generate a list of sample points that are seen from the camera and then project these into light space, much like Alias-free Shadow Maps. In the next step, we analyze the list of sample points on the GPU to construct a tight light frustum for shadow rendering. After the light frustum is computed, we calculate for each sample the actual coverage in the final shadow map to estimate how large a shadow map pixel should be. From this number, we derive the lowest possible resolution to use in the shadow map while retaining nearly alias-free shadows. Our algorithm is built for a deferred renderer.
NetVis: a Visualization Tool Enabling Multiple Perspectives of Network Traffic Data
(The Eurographics Association, 2013) Nicholls, James; Peters, Dominik; Slawinski, Albert; Spoor, Thomas; Vicol, Sergiu; Happa, Jassim; Goldsmith, Michael; Creese, Sadie; Silvester Czanner and Wen Tang
Computer network traffic visualizations deliver improved understanding of pattern-of-life for networks, and such enhanced awareness can facilitate the detection of malicious traffic. Existing tools often opt for graph or plotbased visualizations to detect patterns or outliers in the data, but they still largely provide segmented views. In this paper we present a novel framework designed to support multiple heterogeneous visualizations of network traffic data. NetVis enables different visualizations that work in tandem to provide different perspectives of the same data in real-time. As each visualization is modularly tied together, it enables a user to investigate on-going activity, or any subset of it, at their pace and based on their priorities for further exploration. We currently support six visualizations, three are new and three are based on existing literature (parallel coordinate plots, flowscan and spinning cube of potential doom). Our results show that it is possible to use NetVis to detect unusual activity such as cyber attacks on a network. The framework is written to allow future visualizations to be added straightforwardly.
Acquisition, Representation and Rendering of Real-World Models using Polynomial Texture Maps in 3D
(The Eurographics Association, 2013) Vassallo, Elaine; Spina, Sandro; Debattista, Kurt; Silvester Czanner and Wen Tang
The ability to represent real-world objects digitally in a realistic manner is an indispensable tool for many applications. This paper proposes a method for acquiring, processing, representing, and rendering these digital representations. Acquisition can be divided into two processes: acquiring the 3D geometry of the object, and obtaining the texture and reflectance behaviour of the object. Our work explores the possibility of using Microsoft's Kinect sensor to acquire the 3D geometry, by registration of data captured from different viewpoints. The Kinect sensor itself is used to acquire texture and reflectance information which is represented using multiple Polynomial Texture Maps. We present processing pipelines for both geometry and texture, and finally our work examines how the acquired and processed geometry, texture, and reflectance behaviour information can be mapped together in 3D, allowing the user to view the object from different viewpoints while being able to interactively change light direction. Varying light direction uncovers details of the object which would not have been possible to observe using a single, fixed, light direction. This is useful in many scenarios, amongst which is the examination of cultural heritage artifacts with surface variations.
Measuring Realism in Hair Rendering
(The Eurographics Association, 2013) Ramesh, Girish; Turner, Martin J.; Silvester Czanner and Wen Tang
Visualisation of hair is an extremely complex problem within the field of Computer Graphics. Over the last 10 years, huge strides have been made in the area of physically-based hair rendering, giving rise to many applications in various fields other than the graphics industry. Given the number of models for hair rendering, there is no well defined evaluation process to measure the realism in the hair models in use today. For this work-in-progress paper, we propose an evaluation process not only to evaluate the realism in hair rendering models, but also examine the various effects that contribute to its realistic perception. This builds an index of realism based on experiments with computer generated models, and then proposes comparing the results with values obtained from computational tomography, optical imaging and goniophotometer readings.
Support for the Calculation of Stent Fatigue Fracture in Peripheral Arteries
(The Eurographics Association, 2013) McFarlane, Nigel J. B.; Wei, Hui; Zhao, Youbing; Clapworthy, Gordon J.; Testi, Debora; Chiarini, Alessandro; Silvester Czanner and Wen Tang
Vascular stenting is a medical intervention in which a wire mesh tube is inserted into an artery or vein to provide internal support. This is a safe and common procedure, but stents are now increasingly being deployed in peripheral locations, such as the femoral artery, as part of a procedure called Peripheral Vascular Angioplasty (PVA). Stents in such locations are subject to cyclic bending, and are therefore at risk of fatigue fracture. This paper describes the work of the RT3S project, which brings together stent modelling, surgical simulation and risk calculation for surgical planning. This will allow the clinical user to interactively assess different stent models and deployment options for breakage risk. In the RT3S system, models of several commercial models of self-expanding stent are available for simulation. The placement of the stent in the vessel and the withdrawal of the catheter sheath to expand the stent are visualised. A simplex control mesh is used to guide the deformation of the stent from its compressed start configuration to its expanded final position. The fracture risk for the given model and its patient-specific final position is precomputed using the response surfaces methodology.
Multi-Perspective Detail+Overview Visualization for 3D Building Exploration
(The Eurographics Association, 2013) Pasewaldt, Sebastian; Trapp, Matthias; Döllner, Jürgen; Silvester Czanner and Wen Tang
Virtual 3D building models, as key elements of virtual 3D city models, are used in a growing number of application domains, such as geoanalysis, disaster management and architectural planning. Visualization systems for such building models often rely on perspective or orthogonal projections using a single viewpoint. Therefore, the exploration of a complete model requires a user to change the viewpoint multiple times and to memorize the content of each view to obtain a comprehensive mental model. Since this is usually a time-consuming task, which implies context switching, current visualization systems use multiple viewports to simultaneously depict an object from different perspectives. Our approach extends the idea of multiple viewports by combining two linked views for the interactive exploration of virtual 3D buildings model and their façades. In contrast to traditional approaches, we automatically generate a multi-perspective view that simultaneously depicts all façades of the building in one overview image. This facilitates the process of obtaining overviews and supports fast and direct navigation to various points-of-interest. We describe the concept and implementations of our Multiple-Center-of-Projection camera model for real-time multi-perspective image synthesis. Further, we provide insights into different interaction techniques for linked multi-perspective views and outline approaches of future work.
GPU Simulation of Finite Element Facial Soft-Tissue Models
(The Eurographics Association, 2013) Warburton, Mark; Maddock, Steve; Silvester Czanner and Wen Tang
Physically-based animation techniques enable more realistic and accurate animation to be created. We present a GPU-based finite element (FE) simulation and interactive visualisation system for efficiently producing realisticlooking animations of facial movement, including expressive wrinkles. It is optimised for simulating multi-layered voxel-based models using the total Lagrangian explicit dynamic (TLED) FE method. The flexibility of our system enables detailed animations of gross and fine-scale soft-tissue movement to be easily produced with different muscle structures and material parameters. While we focus on the forehead, the system can be used to animate any multi-material soft body.
A Fast Inverse Kinematics Solver using Intersection of Circles
(The Eurographics Association, 2013) Ramachandran, Srinivasan; John, Nigel W.; Silvester Czanner and Wen Tang
Inverse Kinematics (IK) calculates the joint angles of an articulated object so that its end effector can be positioned as desired. This paper presents an efficient IK method using a geometric solver based on the intersection of circles. For an articulated object with n joints, our method will position the end-effector accurately and requires only a reverse iteration of (n-2). An intuitive user interface is provided, which automatically keeps the end effector between the maximum and minimum extent of the articulated object. Common problems that can occur with other IK methods are avoided. The algorithm has been implemented using WebGL and Javascript and tested by simulating a human hand, a three joint robot arm and human cycling motion, achieving interactive rates of up to 60 FPS
The Evaluation of Perceptual Effectiveness of Isosurface Rendering-based Uncertainty Visualization Techniques for Volumetric Scalar Data
(The Eurographics Association, 2013) Ma, Ji; Murphy, David; Provan, Gregory; O'Mathuna, Cian; Hayes, Michael; Silvester Czanner and Wen Tang
Many techniques have been proposed to convey uncertainty in visualization. However, little research has been reported on the evaluation of their effectiveness.We present a user study that evaluates the perceptual effectiveness of six (four new and two existing) isosurface rendering-based uncertainty visualization techniques. For every technique, we consider its four effectiveness aspects: identification of the data, identification of the uncertainty, visual overload and brightness. There are thirty users participated in the user study and statistical analysis has been made for this study. Our analysis suggested that the two existing uncertainty visualization techniques appear to be the most advantageous in all the evaluated techniques. Both of them have high scores in all the four aspects of the effectiveness. In terms of the new techniques, the transparency technique appears to be the most promising. Whilst the remaining three new techniques may have some utility in certain aspects of the effectiveness, they are less useful in other aspects of the effectiveness. Additionally, a surprising result we have found is that adding auxiliary grid lines as background is not guaranteed to enhance the participants' perception to the errors depicted by the transparency. Conversely, it may lead to visual overload that increases the difficulty to recognize data. We believe that these findings can be useful for future uncertainty visualization design.
A Compact Tucker-Based Factorization Model for Heterogeneous Subsurface Scattering
(The Eurographics Association, 2013) Kurt, Murat; Öztürk, Aydin; Peers, Pieter; Silvester Czanner and Wen Tang
This paper presents a novel compact factored subsurface scattering representation for optically thick, heterogeneous translucent materials. Our subsurface scattering representation is a combination of Tucker-based factorization and a linear regression method. We first apply Tucker factorization on the intensity profiles of the heterogeneous subsurface scattering responses. Next, we fit a polynomial model for characterizing the differences between the different color channels with a linear regression procedure. We show that our method achieves good compression while maintaining visual fidelity. We validate our heterogeneous subsurface scattering representation on various real-world heterogeneous translucent materials, geometries and lighting conditions.
Geometry-based Algorithm for Detection of Asymmetric Tunnels in Protein Molecules
(The Eurographics Association, 2013) Byska, Jan; Jurcik, Adam; Sochor, Jirí; Silvester Czanner and Wen Tang
We present a novel geometry-based method for computing asymmetric tunnels and voids in proteins, approximating their real shape with selected precision. Our method combines ideas from Voronoi and grid based approaches for protein analysis. We represent tunnels in protein using voxel data grid which allows us to store their shape more accurately. Our algorithm employs a tunnel skeleton computed using Voronoi diagram. The skeleton allows us to perform grid computation in a bounded space, with lower time and memory demands, and easily identify and measure individual tunnels.
StegoNPR: Information Hiding in Painterly Renderings
(The Eurographics Association, 2013) Lord, Craig; Collomosse, John; Silvester Czanner and Wen Tang
We present a novel steganographic technique for concealing information within an image. Uniquely we explore the practicality of hiding, and recovering, data within the pattern of brush strokes generated by a non-photorealistic rendering (NPR) algorithm. We incorporate a linear binary coding (LBC) error correction scheme over a raw data channel established through the local statistics of NPR stroke orientations. This enables us to deliver a robust channel for conveying short (e.g. 30 character) strings covertly within a painterly rendering. We evaluate over a variety of painterly renderings, parameter settings and message lengths.

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