VVG03

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https://diglib.eg.org/handle/10.2312/1029

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Lambertian Correction for Rough and Specular Surfaces
(The Eurographics Association, 2003) Robles-Kelly, A.; Hancock, E.R.; Peter Hall and Philip Willis
This paper describes a method for performing Lambertian reflectance for rough and specular surfaces. Rather than using an existing reflectance model, we present a method for estimating the reflectance function from image data. The method makes use of the Gauss map between a surface and a unit sphere. Under conditions in which the light source direction and the viewer direction are identical, we show how the reflectance function can be represented by a polar function on the unit sphere. We pose the problem of recovering the reflectance function as that of estimating a tabular representation of the polar function. A simple analysis shows how the tabular representation of the reflectance function can be obtained using the accumulative distribution of image gradients. By modifying the reflectance function and back-projecting, we can render the surface with alternative lighting models. Here, we choose to back-project a Lambertian reflectance model. This allows us to be remove specularities from shiny surfaces and compensate from boundary ''flattening'' for rough surfaces. We illustrate the utility of the method on a variety of real world imagery.
Investigating Occlusion and Discretization Problems in Image-Based Blurring Techniques
(The Eurographics Association, 2003) Barsky, Brian; Peter Hall and Philip Willis
Traditional computer graphics methods render images that appear sharp at all depths. Adding blur can add realism to a scene, provide a sense of scale, and draw a viewer's attention to a particular region of a scene. Our image based blur algorithm needs to distinguish whether a portion of an image is either from a single object or is part of more than one object. This motivates two approaches to identify objects after an image has been rendered. We illustrate how these techniques can be used in conjunction with our image space method to add blur to a scene.
A Flexible and Versatile Studio for Synchronized Multi-View Video Recording
(The Eurographics Association, 2003) Theobalt, C.; Li, M.; Magnor, M.A.; Seidel, H.-P.; Peter Hall and Philip Willis
In recent years, the convergence of computer vision and computer graphics has put forth new research areas that work on scene reconstruction from and analysis of multi-view video footage. In free-viewpoint video, for example, new views of a scene are generated from an arbitrary viewpoint in real-time using a set of multi-view video streams as inputs. The analysis of real-world scenes from multi-view video to extract motion information or reflection models is another field of research that greatly benefits from high-quality input data. Building a recording setup for multi-view video involves a great effort on the hardware as well as the software side. The amount of image data to be processed is huge, a decent lighting and camera setup is essential for a naturalistic scene appearance and robust background subtraction, and the computing infrastructure has to enable real-time processing of the recorded material. This paper describes our recording setup for multi-view video acquisition that enables the synchronized recording of dynamic scenes from multiple camera positions under controlled conditions. The requirements to the room and their implementation in the separate components of the studio are described in detail. The efficiency and flexibility of the room is demonstrated on the basis of the results that we obtain with a real-time 3D scene reconstruction system, a system for non-intrusive optical motion capture and a model-based free-viewpoint video system for human actors.
3D S.O.M.- A Commercial Software Solution to 3D Scanning
(The Eurographics Association, 2003) Baumberg, A.; Lyons, A.; Taylor, R.; Peter Hall and Philip Willis
This paper describes the novel features of a commercial software-only solution to 3D scanning - the 3D Software Object Modeller (3D S.O.M.). Our work is motivated by the desire to produce a low-cost, portable 3D scanning system based on hand-held digital photographs. We describe the novel techniques we have employed to achieve a robust software-based system in the areas of camera calibration, surface generation and texture extraction.
Real-Time Per-pixel Rendering of Bump-mapped Textures Captured using Photometric Stereo
(The Eurographics Association, 2003) Robb, M.; Spence, A.D.; Chantler, M.J.; Timmins, M.; Peter Hall and Philip Willis
We present recent results from an EPSRC funded project VirTex (Virtual Textile Catalogues). The goal of this project is to develop graphics and image-processing software for the capture, storage, search, retrieval and visualisation of 3D textile samples. The ultimate objective is to develop a web-based application that allows the user to search a database for suitable textiles and to visualise selected samples using real-time photorealistic 3D animation. The innovation in this work is the combined use of photometric stereo and real-time per-pixel rendering for the capture and visualisation of textile samples. Photometric stereo is a simple method that allows both the bump map and the albedo map of a surface texture to be captured digitally. When imported into a standard graphics program these images can be used to provide 3D models with a photorealistic appearance. We have developed software that takes advantage of the advanced rendering features of consumer graphics accelerators to produce bump mapped models in real-time. The viewer can manipulate both viewpoint and lighting to gain a deeper perception of the properties of the textile sample.
Cartoon-Style Rendering of Motion from Video
(The Eurographics Association, 2003) Collomosse, J.P.; Hall, P.M.; Peter Hall and Philip Willis
The contribution of this paper is a novel non-photorealistic rendering (NPR) system capable of rendering motion within a video sequence in artistic styles. A variety of cartoon-style motion cues may be inserted into a video sequence, including augmentation cues (such as streak lines, ghosting, or blurring) and deformation cues (such as squash and stretch or drag effects). Users may select from the gamut of available styles by setting parameters which in uence the placement and appearance of motion cues. Our system draws upon techniques from both the vision and the graphics communities to analyse and render motion and is entirely automatic, aside from minimal user interaction to bootstrap a feature tracker. We demonstrate successful application of our system to a variety of subjects with complexities ranging from simple oscillatory to articulated motion, under both static and moving camera conditions with occlusion present. We conclude with a critical appraisal of the system and discuss directions for future work.
Extending Natural Textures with Multi-Scale Synthesis
(The Eurographics Association, 2003) Stahlhut, O.; Peter Hall and Philip Willis
This paper presents a texture synthesis algorithm that was designed for the tile-less generation of large images of arbitrary size from small sample images. The synthesised texture shows features that are visually similar to the sample over a wide frequency range. The development of the algorithm aimed at achieving high quality results for a large range of natural textures, incorporation of the original samples in the synthesis product, ease of use and good texturing speed even with input sample data two magnitudes larger than used by previous techniques. Like other algorithms we utilise an implicit texture model by copying arbitrary shaped texture patches from the sample to the destination over a multi-scale image pyramid. Our method combines the advantages of different previous techniques with respect to quality. A mixture of exhaustive searching, massive parallel computing and the well-known LBG-algorithm ensures a good balance between texturing quality and speed.
User Interfaces for Mobile Augmented Reality Systems
(The Eurographics Association, 2003) Feiner, Steve; Peter Hall and Philip Willis
What should user interfaces look like when they become an integral part of how we experience the world around us? This talk provides an overview of work that explores user interface design issues for mobile augmented reality systems, which use tracked see-through and hear-through displays to overlay virtual graphics and sound on the real world.
Visualising Video Sequences using Direct Volume Rendering
(The Eurographics Association, 2003) Daniel, G.; Chen, M.; Peter Hall and Philip Willis
It is evident that more and more video data is being generated everyday, for example, by TV broadcast companies and security cameras. However, whilst we are overwhelmed by the huge amount of imagery data, machine vision is generally not yet ready to replace us in most of the everyday visual tasks. In this paper we present a novel approach to the handling of video data. We propose to employ volume visualisation techniques for ''summarising'' video sequences, and to render video volumes into appropriate visual representations. Such visualisations can be used to assist in a decision making process, for instance, to determine if there is any unusual level of activity recorded in a video. In the paper, we present a prototype system, called V3, for capturing, managing, processing and visualising video data sets. We highlight the conceptual similarity between video visualisation and the traditional volume visualisation, and describe the deployment of conventional transfer functions and spatial transfer functions in video visualisation. We examine several statistical image comparison metrics and discuss their effectiveness in extracting meaningful information from video sequences. This work demonstrates the importance and the potential of combining graphics, video and vision technologies.
Models from Image Triplets using Epipolar Gradient Features
(The Eurographics Association, 2003) Vincent, É.; Laganière, R.; Peter Hall and Philip Willis
In an application where sparse matching of feature points is used towards fast scene reconstruction, the choice of the type of features to be matched has an important impact on the quality of the resulting model. In this work, a method is presented for quickly and reliably selecting and matching points from three views of a scene. The selected points are based on epipolar gradients, and consist in stable image features relevant to reconstruction. Then, the selected points are matched using edge transfer, a measure of geometric consistency for point triplets and the edges on which they lie. This matching scheme is invariant to image deformations due to changes in viewpoint. Models drawn from matches obtained by the proposed technique are shown to demonstrate its usefulness.
Prometheus: Facial Modelling, Tracking and Puppetry
(The Eurographics Association, 2003) Thorne, J.M.; Chatting, D.J.; Peter Hall and Philip Willis
The Prometheus project sought to create a real-time production chain for 3D content. This paper summarises the techniques that were developed for facial modelling, tracking and puppetry. The process used for creating photo-realistic models from images of the face is discussed along with the creation of a real-time markerless facial feature tracker, highlighting the methods for extracting pose, detecting the shape of the mouth and interpreting the occurrence of skin wrinkling. The conversion of tracking data to useable animation is also addressed.
Frontiers in 3D Photography: Reflectance and Motion
(The Eurographics Association, 2003) Seitz, Steve; Peter Hall and Philip Willis
The last decade has seen great progress in 3D shape capture technology, both in terms of research ad- vances and successful commercial systems. So why don't most people own 3D cameras? Aside from such issues as expense and size, there remain fundamental technical problems that restrict the applicability of the current state of the art. One of these problems is modeling realistic materials. If you look around, you'll notice that most objects are shiny and have specular highlights. However, virtually all shape recovery methods perform poorly for such surfaces. For this reason, it is common to paint an object white before scanning with a laser scanner. This limitation seems unnecessary, given that the human visual system appears to have no such problem{in fact, highlights should give us more information for shape inference. Another major limitation is that the 3D capture process is currently slow and laborious. In particular, very few techniques exist that can capture moving scenes. Obtaining accurate and complete models of moving scenes is challenging, due to the limited measurements that can be obtained at each instant in time. In this talk, I will describe new work from my research group that seeks to address these two problems{ modeling shiny scenes and moving scenes from photographs. We have recently developed shape capture methods that produce laser-scanner-quality results but for scenes with general re ective properties, including shiny surfaces and even anisotropic materials like brushed fur. I will also describe motion- scanning techniques that yield dense shape reconstructions of moving scenes.
Collaborative Vision and Interactive Mosaicing
(The Eurographics Association, 2003) Robinson, J.A.; Peter Hall and Philip Willis
I propose criteria for collaborative vision applications where a camera user/operator and a computer work together to analyse a scene. An example of how these may be fulfilled is provided in IMP - an interactive mosaicing program.IMP generates mosaics in real-time, interacting with the user to cue camera movement and relay performance in-formation.
A Vision-Based Location System using Fiducials
(The Eurographics Association, 2003) Johnston, D.J.; Clark, A.F.; Peter Hall and Philip Willis
A system for vision-based ego location using 'targets' or 'fiducials' is described. The system is robust and operates on commodity hardware in real time. The accuracy of the system is assessed and found to be good enough to support some augmented reality applications. Two example applications are described: the control of an avatar in a shared virtual environment and a video 'joystick' for manipulating 3D models.
Interpretation of Fuzzy Logic For Texture Queries in CBIR
(The Eurographics Association, 2003) Kulkarni, S.; Peter Hall and Philip Willis
This paper presents a novel fuzzy logic based approach for the interpretation of texture queries. Tamura feature extraction technique is used to extract each texture feature of an image in the database. A term set on each Tamura feature is generated by a fuzzy clustering algorithm to pose a query in terms of natural language. The query can be expressed as a logic combination of natural language terms and tamura feature values. The performance of the technique was evaluated on Brodatz texture benchmark database. Experimental results show that the proposed technique is effective and the retrieved images indicate that those images are suitable for the specific queries.
A Region Adjacency Tree Approach to the Detection and Design of Fiducials
(The Eurographics Association, 2003) Costanza, E.; Robinson, J.; Peter Hall and Philip Willis
We report a topological approach to fiducial recognition for real-time applications. Independence from geometry makes the system tolerant to severe distortion, and allows encoding of extra information. The method is based on region adjacency trees. After describing the mathematical foundations, we present a set of simulations to evaluate the algorithm and optimise the fiducial design.
Towards A 3D Virtual Studio for Human Appearance Capture
(The Eurographics Association, 2003) Starck, J.; Hilton, A.; Peter Hall and Philip Willis
This paper introduces the concept of a ''3D Virtual Studio'' for human appearance capture, akin to the motion capture studio for human motion tracking. Ultimately the 3D Virtual Studio should enable video-realistic reconstruction of a moving person from any viewpoint. A mesh-based stereo technique is presented to reconstruct a moving person from multiple camera views. This technique optimises a surface mesh to match stereo and silhouette data in a constrained coarse-to-fine framework, recovering sub-pixel image correspondence in the presence of inexact camera calibration. We compare this approach for scene reconstruction to conventional shape from silhouette and multiple view stereo. We then demonstrate view-dependent rendering and show improved resolution with the recovered image correspondence. We then demonstrate how this approach can be used to capture the dynamic shape and appearance of a computer graphics model of a person.
An Eigenvector Method for Surface Recovery
(The Eurographics Association, 2003) Robles-Kelly, A.; Hancock, E.R.; Peter Hall and Philip Willis
In this paper we explore how spectral methods for graph seriation can be used to develop a new shape-fromshading algorithm. We characterise the field of surface normals using a transition matrix whose elements are computed from the sectional curvature between different image locations. We use a graph seriation method to define a curvature minimising surface integration path for the purposes of height reconstruction. To smooth the reconstructed surface, we fit quadric patches to the height data. The smoothed surface normal directions are updated ensuring compliance with Lambert's law. The processes of height recovery and surface normal adjustment are interleaved and iterated until a stable surface is obtained. We provide results on synthetic and real-world imagery.
Iterative Multi-Planar Camera Calibration: Improving Stability using Model Selection
(The Eurographics Association, 2003) Vigueras, J.F.; Berger, M.-O.; Simon, G.; Peter Hall and Philip Willis
Tracking, or camera pose determination, is the main technical challenge in numerous applications in computer vision and especially in Augmented Reality. However, pose computation processes commonly exhibit some fluctuations and lack of precision in the estimation of the parameters. This leads to unpleasant visual impressions when augmented scenes are considered. In this paper, we propose an efficient and reliable method for real time camera tracking which avoid unpleasant statistical fluctuations. This method is based on the knowledge of a piecewise planar structure in the scene and makes use of model selection to reduce fluctuations. Videos are attached to this paper which prove the effectiveness of our approach.
Quasi-3D cell-based Animation
(The Eurographics Association, 2003) Qi, M.; Willis, P.J.; Peter Hall and Philip Willis
We present a method for image compositing and rendering using 2D geometric shapes or raster images as input primitives, disposed in a 3D environment around which the camera can move. An animation system has been implemented which calculates camera and scene information to render the frames. The key features of this quasi- 3D system are described. Two animations generated by the system are given as examples.

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