Scalable exploration of 3D massive models

Programa Oficial de Doutoramento en Tecnoloxías da Información e as Comunicacións. 5032V01[Resumo] Esta tese presenta unha serie técnicas escalables que avanzan o estado da arte da creación e exploración de grandes modelos tridimensionaies. No ámbito da xeración destes modelos, preséntanse métodos para mellorar a adquisición e procesado de escenas reais, grazas a unha implementación eficiente dun sistema out- of- core de xestión de nubes de puntos, e unha nova metodoloxía escalable de fusión de datos de xeometría e cor para adquisicións con oclusións. No ámbito da visualización de grandes conxuntos de datos, que é o núcleo principal desta tese, preséntanse dous novos métodos. O primeiro é unha técnica adaptabile out-of-core que aproveita o hardware de rasterización da GPU e as occlusion queries para crear lotes coherentes de traballo, que serán procesados por kernels de trazado de raios codificados en shaders, permitindo out-of-core ray-tracing con sombreado e iluminación global. O segundo é un método de compresión agresivo que aproveita a redundancia xeométrica que se adoita atopar en grandes modelos 3D para comprimir os datos de forma que caiban, nun formato totalmente renderizable, na memoria da GPU. O método está deseñado para representacións voxelizadas de escenas 3D, que son amplamente utilizadas para diversos cálculos como para acelerar as consultas de visibilidade na GPU. A compresión lógrase fusionando subárbores idénticas a través dunha transformación de similitude, e aproveitando a distribución non homoxénea de referencias a nodos compartidos para almacenar punteiros aos nodos fillo, e utilizando unha codificación de bits variable. A capacidade e o rendemento de todos os métodos avalíanse utilizando diversos casos de uso do mundo real de diversos ámbitos e sectores, incluídos o patrimonio cultural, a enxeñería e os videoxogos.[Resumen] En esta tesis se presentan una serie técnicas escalables que avanzan el estado del arte de la creación y exploración de grandes modelos tridimensionales. En el ámbito de la generación de estos modelos, se presentan métodos para mejorar la adquisición y procesado de escenas reales, gracias a una implementación eficiente de un sistema out-of-core de gestión de nubes de puntos, y una nueva metodología escalable de fusión de datos de geometría y color para adquisiciones con oclusiones. Para la visualización de grandes conjuntos de datos, que constituye el núcleo principal de esta tesis, se presentan dos nuevos métodos. El primero de ellos es una técnica adaptable out-of-core que aprovecha el hardware de rasterización de la GPU y las occlusion queries, para crear lotes coherentes de trabajo, que serán procesados por kernels de trazado de rayos codificados en shaders, permitiendo renders out-of-core avanzados con sombreado e iluminación global. El segundo es un método de compresión agresivo, que aprovecha la redundancia geométrica que se suele encontrar en grandes modelos 3D para comprimir los datos de forma que quepan, en un formato totalmente renderizable, en la memoria de la GPU. El método está diseñado para representaciones voxelizadas de escenas 3D, que son ampliamente utilizadas para diversos cálculos como la aceleración las consultas de visibilidad en la GPU o el trazado de sombras. La compresión se logra fusionando subárboles idénticos a través de una transformación de similitud, y aprovechando la distribución no homogénea de referencias a nodos compartidos para almacenar punteros a los nodos hijo, utilizando una codificación de bits variable. La capacidad y el rendimiento de todos los métodos se evalúan utilizando diversos casos de uso del mundo real de diversos ámbitos y sectores, incluidos el patrimonio cultural, la ingeniería y los videojuegos.[Abstract] This thesis introduces scalable techniques that advance the state-of-the-art in massive model creation and exploration. Concerning model creation, we present methods for improving reality-based scene acquisition and processing, introducing an efficient implementation of scalable out-of-core point clouds and a data-fusion approach for creating detailed colored models from cluttered scene acquisitions. The core of this thesis concerns enabling technology for the exploration of general large datasets. Two novel solutions are introduced. The first is an adaptive out-of-core technique exploiting the GPU rasterization pipeline and hardware occlusion queries in order to create coherent batches of work for localized shader-based ray tracing kernels, opening the door to out-of-core ray tracing with shadowing and global illumination. The second is an aggressive compression method that exploits redundancy in large models to compress data so that it fits, in fully renderable format, in GPU memory. The method is targeted to voxelized representations of 3D scenes, which are widely used to accelerate visibility queries on the GPU. Compression is achieved by merging subtrees that are identical through a similarity transform and by exploiting the skewed distribution of references to shared nodes to store child pointers using a variable bitrate encoding The capability and performance of all methods are evaluated on many very massive real-world scenes from several domains, including cultural heritage, engineering, and gaming

A Survey of Geometric Analysis in Cultural Heritage

We present a review of recent techniques for performing geometric analysis in cultural heritage (CH) applications. The survey is aimed at researchers in the areas of computer graphics, computer vision and CH computing, as well as to scholars and practitioners in the CH field. The problems considered include shape perception enhancement, restoration and preservation support, monitoring over time, object interpretation and collection analysis. All of these problems typically rely on an understanding of the structure of the shapes in question at both a local and global level. In this survey, we discuss the different problem forms and review the main solution methods, aided by classification criteria based on the geometric scale at which the analysis is performed and the cardinality of the relationships among object parts exploited during the analysis. We finalize the report by discussing open problems and future perspectives

Scalable Exploration of Complex Objects and Environments Beyond Plain Visual Replication​

Digital multimedia content and presentation means are rapidly increasing their sophistication and are now capable of describing detailed representations of the physical world. 3D exploration experiences allow people to appreciate, understand and interact with intrinsically virtual objects. Communicating information on objects requires the ability to explore them under different angles, as well as to mix highly photorealistic or illustrative presentations of the object themselves with additional data that provides additional insights on these objects, typically represented in the form of annotations. Effectively providing these capabilities requires the solution of important problems in visualization and user interaction. In this thesis, I studied these problems in the cultural heritage-computing-domain, focusing on the very common and important special case of mostly planar, but visually, geometrically, and semantically rich objects. These could be generally roughly flat objects with a standard frontal viewing direction (e.g., paintings, inscriptions, bas-reliefs), as well as visualizations of fully 3D objects from a particular point of views (e.g., canonical views of buildings or statues). Selecting a precise application domain and a specific presentation mode allowed me to concentrate on the well defined use-case of the exploration of annotated relightable stratigraphic models (in particular, for local and remote museum presentation). My main results and contributions to the state of the art have been a novel technique for interactively controlling visualization lenses while automatically maintaining good focus-and-context parameters, a novel approach for avoiding clutter in an annotated model and for guiding users towards interesting areas, and a method for structuring audio-visual object annotations into a graph and for using that graph to improve guidance and support storytelling and automated tours. We demonstrated the effectiveness and potential of our techniques by performing interactive exploration sessions on various screen sizes and types ranging from desktop devices to large-screen displays for a walk-up-and-use museum installation. KEYWORDS - Computer Graphics, Human-Computer Interaction, Interactive Lenses, Focus-and-Context, Annotated Models, Cultural Heritage Computing

Surface Appearance Estimation from Video Sequences

The realistic virtual reproduction of real world objects using Computer Graphics techniques requires the accurate acquisition and reconstruction of both 3D geometry and surface appearance. Unfortunately, in several application contexts, such as Cultural Heritage (CH), the reflectance acquisition can be very challenging due to the type of object to acquire and the digitization conditions. Although several methods have been proposed for the acquisition of object reflectance, some intrinsic limitations still make its acquisition a complex task for CH artworks: the use of specialized instruments (dome, special setup for camera and light source, etc.); the need of highly controlled acquisition environments, such as a dark room; the difficulty to extend to objects of arbitrary shape and size; the high level of expertise required to assess the quality of the acquisition. The Ph.D. thesis proposes novel solutions for the acquisition and the estimation of the surface appearance in fixed and uncontrolled lighting conditions with several degree of approximations (from a perceived near diffuse color to a SVBRDF), taking advantage of the main features that differentiate a video sequences from an unordered photos collections: the temporal coherence; the data redundancy; the easy of the acquisition, which allows acquisition of many views of the object in a short time. Finally, Reflectance Transformation Imaging (RTI) is an example of widely used technology for the acquisition of the surface appearance in the CH field, even if limited to single view Reflectance Fields of nearly flat objects. In this context, the thesis addresses also two important issues in RTI usage: how to provide better and more flexible virtual inspection capabilities with a set of operators that improve the perception of details, features and overall shape of the artwork; how to increase the possibility to disseminate this data and to support remote visual inspection of both scholar and ordinary public

Scalable exploration of highly detailed and annotated 3D models

With the widespread availability of mobile graphics terminals andWebGL-enabled browsers, 3D graphics over the Internet is thriving. Thanks to recent advances in 3D acquisition and modeling systems, high-quality 3D models are becoming increasingly common, and are now potentially available for ubiquitous exploration. In current 3D repositories, such as Blend Swap, 3D Café or Archive3D, 3D models available for download are mostly presented through a few user-selected static images. Online exploration is limited to simple orbiting and/or low-fidelity explorations of simplified models, since photorealistic rendering quality of complex synthetic environments is still hardly achievable within the real-time constraints of interactive applications, especially on on low-powered mobile devices or script-based Internet browsers. Moreover, navigating inside 3D environments, especially on the now pervasive touch devices, is a non-trivial task, and usability is consistently improved by employing assisted navigation controls. In addition, 3D annotations are often used in order to integrate and enhance the visual information by providing spatially coherent contextual information, typically at the expense of introducing visual cluttering. In this thesis, we focus on efficient representations for interactive exploration and understanding of highly detailed 3D meshes on common 3D platforms. For this purpose, we present several approaches exploiting constraints on the data representation for improving the streaming and rendering performance, and camera movement constraints in order to provide scalable navigation methods for interactive exploration of complex 3D environments. Furthermore, we study visualization and interaction techniques to improve the exploration and understanding of complex 3D models by exploiting guided motion control techniques to aid the user in discovering contextual information while avoiding cluttering the visualization. We demonstrate the effectiveness and scalability of our approaches both in large screen museum installations and in mobile devices, by performing interactive exploration of models ranging from 9Mtriangles to 940Mtriangles

Surface analysis and visualization from multi-light image collections

Multi-Light Image Collections (MLICs) are stacks of photos of a scene acquired with a fixed viewpoint and a varying surface illumination that provides large amounts of visual and geometric information. Over the last decades, a wide variety of methods have been devised to extract information from MLICs and have shown its use in different application domains to support daily activities. In this thesis, we present methods that leverage a MLICs for surface analysis and visualization. First, we provide background information: acquisition setup, light calibration and application areas where MLICs have been successfully used for the research of daily analysis work. Following, we discuss the use of MLIC for surface visualization and analysis and available tools used to support the analysis. Here, we discuss methods that strive to support the direct exploration of the captured MLIC, methods that generate relightable models from MLIC, non-photorealistic visualization methods that rely on MLIC, methods that estimate normal map from MLIC and we point out visualization tools used to do MLIC analysis. In chapter 3 we propose novel benchmark datasets (RealRTI, SynthRTI and SynthPS) that can be used to evaluate algorithms that rely on MLIC and discusses available benchmark for validation of photometric algorithms that can be also used to validate other MLIC-based algorithms. In chapter 4, we evaluate the performance of different photometric stereo algorithms using SynthPS for cultural heritage applications. RealRTI and SynthRTI have been used to evaluate the performance of (Neural)RTI method. Then, in chapter 5, we present a neural network-based RTI method, aka NeuralRTI, a framework for pixel-based encoding and relighting of RTI data. In this method using a simple autoencoder architecture, we show that it is possible to obtain a highly compressed representation that better preserves the original information and provides increased quality of virtual images relighted from novel directions, particularly in the case of challenging glossy materials. Finally, in chapter 6, we present a method for the detection of crack on the surface of paintings from multi-light image acquisitions and that can be used as well on single images and conclude our presentation

Moving sounds and sonic moves : exploring interaction quality of embodied music mediation technologies through a user-centered perspective

This research project deals with the user-experience related to embodied music mediation technologies. More specifically, adoption and policy problems surrounding new media (art) are considered, which arise from the usability issues that to date pervade new interfaces for musical expression. Since the emergence of new wireless mediators and control devices for musical expression, there is an explicit aspiration of the creative industries and various research centers to embed such technologies into different areas of the cultural industries. The number of applications and their uses have exponentially increased over the last decade. Conversely, many of the applications to date still suffer from severe usability problems, which not only hinder the adoption by the cultural sector, but also make culture participants take a rather cautious, hesitant, or even downright negative stance towards these technologies. Therefore, this thesis takes a vantage point that is in part sociological in nature, yet has a link to cultural studies as well. It combines this with a musicological frame of reference to which it introduces empirical user-oriented approaches, predominantly taken from the field of human-computer-interaction studies. This interdisciplinary strategy is adopted to cope with the complex nature of digital embodied music controlling technologies. Within the Flanders cultural (and creative) industries, opportunities of systems affiliated with embodied interaction are created and examined. This constitutes an epistemological jigsaw that looks into 1) “which stakeholders require what various levels of involvement, what interactive means and what artistic possibilities?”, 2) “the way in which artistic aspirations, cultural prerequisites and operational necessities of (prospective) users can be defined?”, 3) “how functional, artistic and aesthetic requirements can be accommodated?”, and 4) “how quality of use and quality of experience can be achieved, quantified, evaluated and, eventually, improved?”. Within this multi-facetted problem, the eventual aim is to assess the applicability of the foresaid technology, both from a theoretically and empirically sound basis, and to facilitate widening and enhancing the adoption of said technologies. Methodologically, this is achieved by 1) applied experimentation, 2) interview techniques, 3) self-reporting and survey research, 4) usability evaluation of existing devices, and 5) human-computer interaction methods applied – and attuned – to the specific case of embodied music mediation technologies. Within that scope, concepts related to usability, flow, presence, goal assessment and game enjoyment are scrutinized and applied, and both task- and experience-oriented heuristics and metrics are developed and tested. In the first part, covering three chapters, the general context of the thesis is given. In the first chapter, an introduction to the topic is offered and the current problems are enumerated. In the second chapter, a broader theoretical background is presented of the concepts that underpin the project, namely 1) the paradigm of embodiment and its connection to musicology, 2) a state of the arts concerning new interfaces for musical expression, 3) an introduction into HCI-usability and its application domain in systematic musicology, 4) an insight into user-centered digital design procedures, and 5) the challenges brought about by e-culture and digitization for the cultural-creative industries. In the third chapter, the state of the arts concerning the available methodologies related to the thesis’ endeavor is discussed, a set of literature-based design guidelines are enumerated and from this a conceptual model is deduced which is gradually presented throughout the thesis, and fully deployed in the “SoundField”-project (as described in Chapter 9). The following chapters, contained in the second part of the thesis, give a quasi-chronological overview of how methodological concepts have been applied throughout the empirical case studies, aimed specifically at the exploration of the various aspects of the complex status quaestionis. In the fourth chapter, a series of application-based tests, predominantly revolving around interface evaluation, illustrate the complex relation between gestural interfaces and meaningful musical expression, advocating a more user-centered development approach to be adopted. In the fifth chapter, a multi-purpose questionnaire dubbed “What Moves You” is discussed, which aimed at creating a survey of the (prospective) end-users of embodied music mediation technologies. Therefore, it primarily focused on cultural background, musical profile and preferences, views on embodied interaction, literacy of and attitudes towards new technology and participation in digital culture. In the sixth chapter, the ethnographical studies that accompanied the exhibition of two interactive art pieces, entitled "Heart as an Ocean" & "Lament", are discussed. In these studies, the use of interview and questionnaire methodologies together with the presentation and reception of interactive art pieces, are probed. In the seventh chapter, the development of the collaboratively controlled music-game “Sync-In-Team” is presented, in which interface evaluation, presence, game enjoyment and goal assessment are the pivotal topics. In the eighth chapter, two usability studies are considered, that were conducted on prototype systems/interfaces, namely a heuristic evaluation of the “Virtual String” and a usability metrics evaluation on the “Multi-Level Sonification Tool”. The findings of these two studies in conjunction with the exploratory studies performed in association with the interactive art pieces, finally gave rise to the “SoundField”-project, which is recounted in full throughout the ninth chapter. The integrated participatory design and evaluation method, presented in the conceptual model is fully applied over the course of the “SoundField”-project, in which technological opportunities and ecological validity and applicability are investigated through user-informed development of numerous use cases. The third and last part of the thesis renders the final conclusions of this research project. The tenth chapter sets out with an epilogue in which a brief overview is given on how the state of the arts has evolved since the end of the project (as the research ended in 2012, but the research field has obviously moved on), and attempts to consolidate the implications of the research studies with some of the realities of the Flemish cultural-creative industries. Chapter eleven continues by discussing the strengths and weaknesses of the conceptual model throughout the various stages of the project. Also, it comprises the evaluation of the hypotheses, how the assumptions that were made held up, and how the research questions eventually could be assessed. Finally, the twelfth and last chapter concludes with the most important findings of the project. Also, it discusses some of the implications on cultural production, artistic research policy and offers an outlook on future research beyond the scope of the “SoundField” project