Volumetric Cell-and-Portal Generation

International audienceWe present an algorithm to generate a cell-and-portal decomposition of general indoor scenes. The method is an adaptation of the 3D watershed transform, computed on a distance-to-geometry sampled field. The watershed is processed using a flooding analogy in the distance field space. Flooding originates from local minima, each minimum producing a region. Portals are built as needed to avoid the merging of regions during their growth. As a result, the cell it deals with parametric curves, implicit surfaces, volumetric data and polygon soups in a unified way

Interactive illumination and navigation control in an image-based environment.

Fu Chi-wing.Thesis (M.Phil.)--Chinese University of Hong Kong, 1999.Includes bibliographical references (leaves 141-149).Abstract --- p.iAcknowledgments --- p.iiiChapter 1 --- Introduction --- p.1Chapter 1.1 --- Introduction to Image-based Rendering --- p.1Chapter 1.2 --- Scene Complexity Independent Property --- p.2Chapter 1.3 --- Application of this Research Work --- p.3Chapter 1.4 --- Organization of this Thesis --- p.4Chapter 2 --- Illumination Control --- p.7Chapter 2.1 --- Introduction --- p.7Chapter 2.2 --- Apparent BRDF of Pixel --- p.8Chapter 2.3 --- Sampling Illumination Information --- p.11Chapter 2.4 --- Re-rendering --- p.13Chapter 2.4.1 --- Light Direction --- p.15Chapter 2.4.2 --- Light Intensity --- p.15Chapter 2.4.3 --- Multiple Light Sources --- p.15Chapter 2.4.4 --- Type of Light Sources --- p.18Chapter 2.5 --- Data Compression --- p.22Chapter 2.5.1 --- Intra-pixel coherence --- p.22Chapter 2.5.2 --- Inter-pixel coherence --- p.22Chapter 2.6 --- Implementation and Result --- p.22Chapter 2.6.1 --- An Interactive Viewer --- p.22Chapter 2.6.2 --- Lazy Re-rendering --- p.24Chapter 2.7 --- Conclusion --- p.24Chapter 3 --- Navigation Control - Triangle-based Warping Rule --- p.29Chapter 3.1 --- Introduction to Navigation Control --- p.29Chapter 3.2 --- Related Works --- p.30Chapter 3.3 --- Epipolar Geometry (Perspective Projection Manifold) --- p.31Chapter 3.4 --- Drawing Order for Pixel-Sized Entities --- p.35Chapter 3.5 --- Triangle-based Image Warping --- p.36Chapter 3.5.1 --- Image-based Triangulation --- p.36Chapter 3.5.2 --- Image-based Visibility Sorting --- p.40Chapter 3.5.3 --- Topological Sorting --- p.44Chapter 3.6 --- Results --- p.46Chapter 3.7 --- Conclusion --- p.48Chapter 4 --- Panoramic Projection Manifold --- p.52Chapter 4.1 --- Epipolar Geometry (Spherical Projection Manifold) --- p.53Chapter 4.2 --- Image Triangulation --- p.56Chapter 4.2.1 --- Optical Flow --- p.56Chapter 4.2.2 --- Image Gradient and Potential Function --- p.57Chapter 4.2.3 --- Triangulation --- p.58Chapter 4.3 --- Image-based Visibility Sorting --- p.58Chapter 4.3.1 --- Mapping Criteria --- p.58Chapter 4.3.2 --- Ordering of Two Triangles --- p.59Chapter 4.3.3 --- Graph Construction and Topological Sort --- p.63Chapter 4.4 --- Results --- p.63Chapter 4.5 --- Conclusion --- p.65Chapter 5 --- Panoramic-based Navigation using Real Photos --- p.69Chapter 5.1 --- Introduction --- p.69Chapter 5.2 --- System Overview --- p.71Chapter 5.3 --- Correspondence Matching --- p.72Chapter 5.3.1 --- Basic Model of Epipolar Geometry --- p.72Chapter 5.3.2 --- Epipolar Geometry between two Neighbor Panoramic Nodes --- p.73Chapter 5.3.3 --- Line and Patch Correspondence Matching --- p.74Chapter 5.4 --- Triangle-based Warping --- p.75Chapter 5.4.1 --- Why Warp Triangle --- p.75Chapter 5.4.2 --- Patch and Layer Construction --- p.76Chapter 5.4.3 --- Triangulation and Mesh Subdivision --- p.76Chapter 5.4.4 --- Layered Triangle-based Warping --- p.77Chapter 5.5 --- Implementation --- p.78Chapter 5.5.1 --- Image Sampler and Panoramic Stitcher --- p.78Chapter 5.5.2 --- Interactive Correspondence Matcher and Triangulation --- p.79Chapter 5.5.3 --- Basic Panoramic Viewer --- p.79Chapter 5.5.4 --- Formulating Drag Vector and vn --- p.80Chapter 5.5.5 --- Controlling Walkthrough Parameter --- p.82Chapter 5.5.6 --- Interactive Web-based Panoramic Viewer --- p.83Chapter 5.6 --- Results --- p.84Chapter 5.7 --- Conclusion and Possible Enhancements --- p.84Chapter 6 --- Compositing Warped Images for Object-based Viewing --- p.89Chapter 6.1 --- Modeling Object-based Viewing --- p.89Chapter 6.2 --- Triangulation and Convex Hull Criteria --- p.92Chapter 6.3 --- Warping Multiple Views --- p.94Chapter 6.3.1 --- Method I --- p.95Chapter 6.3.2 --- Method II --- p.95Chapter 6.3.3 --- Method III --- p.95Chapter 6.4 --- Results --- p.97Chapter 6.5 --- Conclusion --- p.100Chapter 7 --- Complete Rendering Pipeline --- p.107Chapter 7.1 --- Reviews on Illumination and Navigation --- p.107Chapter 7.1.1 --- Illumination Rendering Pipeline --- p.107Chapter 7.1.2 --- Navigation Rendering Pipeline --- p.108Chapter 7.2 --- Analysis of the Two Rendering Pipelines --- p.109Chapter 7.2.1 --- Combination on the Architectural Level --- p.109Chapter 7.2.2 --- Ensuring Physical Correctness --- p.111Chapter 7.3 --- Generalizing Apparent BRDF --- p.112Chapter 7.3.1 --- Difficulties to Encode BRDF with Spherical Harmonics --- p.112Chapter 7.3.2 --- Generalize Apparent BRDF --- p.112Chapter 7.3.3 --- Related works for Encoding the generalized apparent BRDF --- p.113Chapter 7.4 --- Conclusion --- p.116Chapter 8 --- Conclusion --- p.117Chapter A --- Spherical Harmonics --- p.120Chapter B --- It is Rare for Cycles to Exist in the Drawing Order Graph --- p.123Chapter B.1 --- Theorem 3 --- p.123Chapter B.2 --- Inside and Outside-directed Triangles in a Triangular Cycle --- p.125Chapter B.2.1 --- Assumption --- p.126Chapter B.2.2 --- Inside-directed and Outside-directed triangles --- p.126Chapter B.3 --- Four Possible Cases to Form a Cycle --- p.127Chapter B.3.1 --- Case(l) Triangular Fan --- p.128Chapter B.3.2 --- Case(2) Two Outside-directed Triangles --- p.129Chapter B.3.3 --- Case(3) Three Outside-directed Triangles --- p.130Chapter B.3.4 --- Case(4) More than Three Outside-directed Triangles --- p.131Chapter B.4 --- Experiment --- p.132Chapter C --- Deriving the Epipolar Line Formula on Cylindrical Projection Manifold --- p.133Chapter C.1 --- Notations --- p.133Chapter C.2 --- General Formula --- p.134Chapter C.3 --- Simplify the General Formula to a Sine Curve --- p.137Chapter C.4 --- Show that the Epipolar Line is a Sine Curve Segment --- p.139Chapter D --- Publications Related to this Research Work --- p.141Bibliography --- p.14

Analysis of urban morphology for real time visualization of urban scenes

Thesis (S.B. and M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1998.Includes bibliographical references (leaves 122-127).by Sami Mohammed Shalabi.S.B.and M.Eng

Point based graphics rendering with unified scalability solutions.

Standard real-time 3D graphics rendering algorithms use brute force polygon rendering, with complexity linear in the number of polygons and little regard for limiting processing to data that contributes to the image. Modern hardware can now render smaller scenes to pixel levels of detail, relaxing surface connectivity requirements. Sub-linear scalability optimizations are typically self-contained, requiring specific data structures, without shared functions and data. A new point based rendering algorithm 'Canopy' is investigated that combines multiple typically sub-linear scalability solutions, using a small core of data structures. Specifically, locale management, hierarchical view volume culling, backface culling, occlusion culling, level of detail and depth ordering are addressed. To demonstrate versatility further, shadows and collision detection are examined. Polygon models are voxelized with interpolated attributes to provide points. A scene tree is constructed, based on a BSP tree of points, with compressed attributes. The scene tree is embedded in a compressed, partitioned, procedurally based scene graph architecture that mimics conventional systems with groups, instancing, inlines and basic read on demand rendering from backing store. Hierarchical scene tree refinement constructs an image tree image space equivalent, with object space scene node points projected, forming image node equivalents. An image graph of image nodes is maintained, describing image and object space occlusion relationships, hierarchically refined with front to back ordering to a specified threshold whilst occlusion culling with occluder fusion. Visible nodes at medium levels of detail are refined further to rasterization scales. Occlusion culling defines a set of visible nodes that can support caching for temporal coherence. Occlusion culling is approximate, possibly not suiting critical applications. Qualities and performance are tested against standard rendering. Although the algorithm has a 0(f) upper bound in the scene sizef, it is shown to practically scale sub-linearly. Scenes with several hundred billion polygons conventionally, are rendered at interactive frame rates with minimal graphics hardware support

FACING EXPERIENCE: A PAINTER’S CANVAS IN VIRTUAL REALITY

Full version unavailable due to 3rd party copyright restrictions.This research investigates how shifts in perception might be brought about through the development of visual imagery created by the use of virtual environment technology. Through a discussion of historical uses of immersion in art, this thesis will explore how immersion functions and why immersion has been a goal for artists throughout history. It begins with a discussion of ancient cave drawings and the relevance of Plato’s Allegory of the Cave. Next it examines the biological origins of “making special.” The research will discuss how this concept, combined with the ideas of “action” and “reaction,” has reinforced the view that art is fundamentally experiential rather than static. The research emphasizes how present-day virtual environment art, in providing a space that engages visitors in computer graphics, expands on previous immersive artistic practices. The thesis examines the technical context in which the research occurs by briefly describing the use of computer science technologies, the fundamentals of visual arts practices, and the importance of aesthetics in new media and provides a description of my artistic practice. The aim is to investigate how combining these approaches can enhance virtual environments as artworks. The computer science of virtual environments includes both hardware and software programming. The resultant virtual environment experiences are technologically dependent on the types of visual displays being used, including screens and monitors, and their subsequent viewing affordances. Virtual environments fill the field of view and can be experienced with a head mounted display (HMD) or a large screen display. The sense of immersion gained through the experience depends on how tracking devices and related peripheral devices are used to facilitate interaction. The thesis discusses visual arts practices with a focus on how illusions shift our cognition and perception in the visual modalities. This discussion includes how perceptual thinking is the foundation of art experiences, how analogies are the foundation of cognitive experiences and how the two intertwine in art experiences for virtual environments. An examination of the aesthetic strategies used by artists and new media critics are presented to discuss new media art. This thesis investigates the visual elements used in virtual environments and prescribes strategies for creating art for virtual environments. Methods constituting a unique virtual environment practice that focuses on visual analogies are discussed. The artistic practice that is discussed as the basis for this research also concentrates on experiential moments and shifts in perception and cognition and references Douglas Hofstadter, Rudolf Arnheim and John Dewey. iv Virtual environments provide for experiences in which the imagery generated updates in real time. Following an analysis of existing artwork and critical writing relative to the field, the process of inquiry has required the creation of artworks that involve tracking systems, projection displays, sound work, and an understanding of the importance of the visitor. In practice, the research has shown that the visitor should be seen as an interlocutor, interacting from a first-person perspective with virtual environment events, where avatars or other instrumental intermediaries, such as guns, vehicles, or menu systems, do not to occlude the view. The aesthetic outcomes of this research are the result of combining visual analogies, real time interactive animation, and operatic performance in immersive space. The environments designed in this research were informed initially by paintings created with imagery generated in a hypnopompic state or during the moments of transitioning from sleeping to waking. The drawings often emphasize emotional moments as caricatures and/or elements of the face as seen from a number of perspectives simultaneously, in the way of some cartoons, primitive artwork or Cubist imagery. In the imagery, the faces indicate situations, emotions and confrontations which can offer moments of humour and reflective exploration. At times, the faces usurp the space and stand in representation as both face and figure. The power of the placement of the caricatures in the paintings become apparent as the imagery stages the expressive moment. The placement of faces sets the scene, establishes relationships and promotes the honesty and emotions that develop over time as the paintings are scrutinized. The development process of creating virtual environment imagery starts with hand drawn sketches of characters, develops further as paintings on “digital canvas”, are built as animated, three-dimensional models and finally incorporated into a virtual environment. The imagery is generated while drawing, typically with paper and pencil, in a stream of consciousness during the hypnopompic state. This method became an aesthetic strategy for producing a snappy straightforward sketch. The sketches are explored further as they are worked up as paintings. During the painting process, the figures become fleshed out and their placement on the page, in essence brings them to life. These characters inhabit a world that I explore even further by building them into three dimensional models and placing them in computer generated virtual environments. The methodology of developing and placing the faces/figures became an operational strategy for building virtual environments. In order to open up the range of art virtual environments, and develop operational strategies for visitors’ experience, the characters and their facial features are used as navigational strategies, signposts and methods of wayfinding in order to sustain a stream of consciousness type of navigation. Faces and characters were designed to represent those intimate moments of self-reflection and confrontation that occur daily within ourselves and with others. They sought to reflect moments of wonderment, hurt, curiosity and humour that could subsequently be relinquished for more practical or purposeful endeavours. They were intended to create conditions in which visitors might reflect upon their emotional state, v enabling their understanding and trust of their personal space, in which decisions are made and the nature of world is determined. In order to extend the split-second, frozen moment of recognition that a painting affords, the caricatures and their scenes are given new dimensions as they become characters in a performative virtual reality. Emotables, distinct from avatars, are characters confronting visitors in the virtual environment to engage them in an interactive, stream of consciousness, non-linear dialogue. Visitors are also situated with a role in a virtual world, where they were required to adapt to the language of the environment in order to progress through the dynamics of a drama. The research showed that imagery created in a context of whimsy and fantasy could bring ontological meaning and aesthetic experience into the interactive environment, such that emotables or facially expressive computer graphic characters could be seen as another brushstroke in painting a world of virtual reality

Presence 2005: the eighth annual international workshop on presence, 21-23 September, 2005 University College London (Conference proceedings)

OVERVIEW (taken from the CALL FOR PAPERS) Academics and practitioners with an interest in the concept of (tele)presence are invited to submit their work for presentation at PRESENCE 2005 at University College London in London, England, September 21-23, 2005. The eighth in a series of highly successful international workshops, PRESENCE 2005 will provide an open discussion forum to share ideas regarding concepts and theories, measurement techniques, technology, and applications related to presence, the psychological state or subjective perception in which a person fails to accurately and completely acknowledge the role of technology in an experience, including the sense of 'being there' experienced by users of advanced media such as virtual reality. The concept of presence in virtual environments has been around for at least 15 years, and the earlier idea of telepresence at least since Minsky's seminal paper in 1980. Recently there has been a burst of funded research activity in this area for the first time with the European FET Presence Research initiative. What do we really know about presence and its determinants? How can presence be successfully delivered with today's technology? This conference invites papers that are based on empirical results from studies of presence and related issues and/or which contribute to the technology for the delivery of presence. Papers that make substantial advances in theoretical understanding of presence are also welcome. The interest is not solely in virtual environments but in mixed reality environments. Submissions will be reviewed more rigorously than in previous conferences. High quality papers are therefore sought which make substantial contributions to the field. Approximately 20 papers will be selected for two successive special issues for the journal Presence: Teleoperators and Virtual Environments. PRESENCE 2005 takes place in London and is hosted by University College London. The conference is organized by ISPR, the International Society for Presence Research and is supported by the European Commission's FET Presence Research Initiative through the Presencia and IST OMNIPRES projects and by University College London

Vertex classification for non-uniform geometry reduction.

Complex models created from isosurface extraction or CAD and highly accurate 3D models produced from high-resolution scanners are useful, for example, for medical simulation, Virtual Reality and entertainment. Often models in general require some sort of manual editing before they can be incorporated in a walkthrough, simulation, computer game or movie. The visualization challenges of a 3D editing tool may be regarded as similar to that of those of other applications that include an element of visualization such as Virtual Reality. However the rendering interaction requirements of each of these applications varies according to their purpose. For rendering photo-realistic images in movies computer farms can render uninterrupted for weeks, a 3D editing tool requires fast access to a model's fine data. In Virtual Reality rendering acceleration techniques such as level of detail can temporarily render parts of a scene with alternative lower complexity versions in order to meet a frame rate tolerable for the user. These alternative versions can be dynamic increments of complexity or static models that were uniformly simplified across the model by minimizing some cost function. Scanners typically have a fixed sampling rate for the entire model being scanned, and therefore may generate large amounts of data in areas not of much interest or that contribute little to the application at hand. It is therefore desirable to simplify such models non-uniformly. Features such as very high curvature areas or borders can be detected automatically and simplified differently to other areas without any interaction or visualization. However a problem arises when one wishes to manually select features of interest in the original model to preserve and create stand alone, non-uniformly reduced versions of large models, for example for medical simulation. To inspect and view such models the memory requirements of LoD representations can be prohibitive and prevent storage of a model in main memory. Furthermore, although asynchronous rendering of a base simplified model ensures a frame rate tolerable to the user whilst detail is paged, no guarantees can be made that what the user is selecting is at the original resolution of the model or of an appropriate LoD owing to disk lag or the complexity of a particular view selected by the user. This thesis presents an interactive method in the con text of a 3D editing application for feature selection from any model that fits in main memory. We present a new compression/decompression of triangle normals and colour technique which does not require dedicated hardware that allows for 87.4% memory reduction and allows larger models to fit in main memory with at most 1.3/2.5 degrees of error on triangle normals and to be viewed interactively. To address scale and available hardware resources, we reference a hierarchy of volumes of different sizes. The distances of the volumes at each level of the hierarchy to the intersection point of the line of sight with the model are calculated and these distances sorted. At startup an appropriate level of the tree is automatically chosen by separating the time required for rendering from that required for sorting and constraining the latter according to the resources available. A clustered navigation skin and depth buffer strategy allows for the interactive visualisation of models of any size, ensuring that triangles from the closest volumes are rendered over the navigation skin even when the clustered skin may be closer to the viewer than the original model. We show results with scanned models, CAD, textured models and an isosurface. This thesis addresses numerical issues arising from the optimisation of cost functions in LoD algorithms and presents a semi-automatic solution for selection of the threshold on the condition number of the matrix to be inverted for optimal placement of the new vertex created by an edge collapse. We show that the units in which a model is expressed may inadvertently affect the condition of these matrices, hence affecting the evaluation of different LoD methods with different solvers. We use the same solver with an automatically calibrated threshold to evaluate different uniform geometry reduction techniques. We then present a framework for non-uniform reduction of regular scanned models that can be used in conjunction with a variety of LoD algorithms. The benefits of non-uniform reduction are presented in the context of an animation system. (Abstract shortened by UMI.)

Sculpting Unrealities: Using Machine Learning to Control Audiovisual Compositions in Virtual Reality

This thesis explores the use of interactive machine learning (IML) techniques to control audiovisual compositions within the emerging medium of virtual reality (VR). Accompanying the text is a portfolio of original compositions and open-source software. These research outputs represent the practical elements of the project that help to shed light on the core research question: how can IML techniques be used to control audiovisual compositions in VR? In order to find some answers to this question, it was broken down into its constituent elements. To situate the research, an exploration of the contemporary field of audiovisual art locates the practice between the areas of visual music and generative AV. This exploration of the field results in a new method of categorising the constituent practices. The practice of audiovisual composition is then explored, focusing on the concept of equality. It is found that, throughout the literature, audiovisual artists aim to treat audio and visual material equally. This is interpreted as a desire for balance between the audio and visual material. This concept is then examined in the context of VR. A feeling of presence is found to be central to this new medium and is identified as an important consideration for the audiovisual composer in addition to the senses of sight and sound. Several new terms are formulated which provide the means by which the compositions within the portfolio are analysed. A control system, based on IML techniques, is developed called the Neural AV Mapper. This is used to develop a compositional methodology through the creation of several studies. The outcomes from these studies are incorporated into two live performance pieces, Ventriloquy I and Ventriloquy II. These pieces showcase the use of IML techniques to control audiovisual compositions in a live performance context. The lessons learned from these pieces are incorporated into the development of the ImmersAV toolkit. This open-source software toolkit was built specifically to allow for the exploration of the IML control paradigm within VR. The toolkit provides the means by which the immersive audiovisual compositions, Obj_#3 and Ag Fás Ar Ais Arís are created. Obj_#3 takes the form of an immersive audiovisual sculpture that can be manipulated in real-time by the user. The title of the thesis references the physical act of sculpting audiovisual material. It also refers to the ability of VR to create alternate realities that are not bound to the physics of real-life. This exploration of unrealities emerges as an important aspect of the medium. The final piece in the portfolio, Ag Fás Ar Ais Arís takes the knowledge gained from the earlier work and pushes the boundaries to maximise the potential of the medium and the material

Biometric Systems

Because of the accelerating progress in biometrics research and the latest nation-state threats to security, this book's publication is not only timely but also much needed. This volume contains seventeen peer-reviewed chapters reporting the state of the art in biometrics research: security issues, signature verification, fingerprint identification, wrist vascular biometrics, ear detection, face detection and identification (including a new survey of face recognition), person re-identification, electrocardiogram (ECT) recognition, and several multi-modal systems. This book will be a valuable resource for graduate students, engineers, and researchers interested in understanding and investigating this important field of study

Motifs, textures and folds: Japanese popular visual culture as transcultural and phenomenological flow

Since the 1980s, Japanese popular visual culture has known great popularity in Western Europe and North America, most strikingly in the form of manga, anime and Japanese video games. However, one is struck by how fragmented this cultural flow is: not only is it composed of three different media, but it also contains works that are wildly different from one another. Can something be said to connect these works together, other than their Japanese provenance? This dissertation proposes two avenues for answering this question and establishing a certain cohesiveness within the fabric of Japanese popular visual culture as it has been exported: on the one hand, this thesis explores recurrent content and themes (motifs) within a purposefully varied corpus of manga, anime and games; on the other, it establishes phenomenological consistencies (textures and folds) across the corpus, demonstrating that these works provide medium-based experiences that are similar in significant respects. Parallel to this demonstration, this dissertation examines the effects of this cohesion on the Western reception of these works. The author argues that, while cultural motifs evoking “Japaneseness” play an initial part in gathering these works into a perceived flow, it is their common phenomenology that cements their perceived cohesion and facilitates their integration into non-Japanese imaginaries. By analysing the transcultural travels of Japanese popular visual culture, this thesis examines a case where differentiated imaginaries meet and merge, and thereby develops a theory of the imaginary as phenomenological and processual space, as a fabric that surrounds us and which we collectively and continually weave and unravel. Ultimately, the author determines that this particular imaginary is regulated by two key notions: on the one hand, a dynamic of flux and stasis, and on the other, a series of interconnected and intermingled folds