Meshless Mechanics and Point-Based Visualization Methods for Surgical Simulations

Computer-based modeling and simulation practices have become an integral part of the medical education field. For surgical simulation applications, realistic constitutive modeling of soft tissue is considered to be one of the most challenging aspects of the problem, because biomechanical soft-tissue models need to reflect the correct elastic response, have to be efficient in order to run at interactive simulation rates, and be able to support operations such as cuts and sutures. Mesh-based solutions, where the connections between the individual degrees of freedom (DoF) are defined explicitly, have been the traditional choice to approach these problems. However, when the problem under investigation contains a discontinuity that disrupts the connectivity between the DoFs, the underlying mesh structure has to be reconfigured in order to handle the newly introduced discontinuity correctly. This reconfiguration for mesh-based techniques is typically called dynamic remeshing, and most of the time it causes the performance bottleneck in the simulation. In this dissertation, the efficiency of point-based meshless methods is investigated for both constitutive modeling of elastic soft tissues and visualization of simulation objects, where arbitrary discontinuities/cuts are applied to the objects in the context of surgical simulation. The point-based deformable object modeling problem is examined in three functional aspects: modeling continuous elastic deformations with, handling discontinuities in, and visualizing a point-based object. Algorithmic and implementation details of the presented techniques are discussed in the dissertation. The presented point-based techniques are implemented as separate components and integrated into the open-source software framework SOFA. The presented meshless continuum mechanics model of elastic tissue were verified by comparing it to the Hertzian non-adhesive frictionless contact theory. Virtual experiments were setup with a point-based deformable block and a rigid indenter, and force-displacement curves obtained from the virtual experiments were compared to the theoretical solutions. The meshless mechanics model of soft tissue and the integrated novel discontinuity treatment technique discussed in this dissertation allows handling cuts of arbitrary shape. The implemented enrichment technique not only modifies the internal mechanics of the soft tissue model, but also updates the point-based visual representation in an efficient way preventing the use of costly dynamic remeshing operations

Substitutional reality:using the physical environment to design virtual reality experiences

Experiencing Virtual Reality in domestic and other uncontrolled settings is challenging due to the presence of physical objects and furniture that are not usually defined in the Virtual Environment. To address this challenge, we explore the concept of Substitutional Reality in the context of Virtual Reality: a class of Virtual Environments where every physical object surrounding a user is paired, with some degree of discrepancy, to a virtual counterpart. We present a model of potential substitutions and validate it in two user studies. In the first study we investigated factors that affect participants' suspension of disbelief and ease of use. We systematically altered the virtual representation of a physical object and recorded responses from 20 participants. The second study investigated users' levels of engagement as the physical proxy for a virtual object varied. From the results, we derive a set of guidelines for the design of future Substitutional Reality experiences

Sensory factors for brand success

In a market, where the features and quality of many products are more or less equal, companies must overcome aesthetic, moral and emotional demands to stand out and be successful (Morsing, 2002). The visual sense has been the emphasized sense for branding and communication of identity (Lindstrom, 2005 a). Human beings, however, are creatures of five senses. Utilization of other sensory impulses than the visual may create a synergetic effect for communication of a company’s identity. It may enhance emotional engagement and loyalty between a company or brand and their interested parties (ibid). Finding or creating a distinct and evident identity is a complicated task. Several authors describe methods that can guide such a process. We suggest that systematic methods presented by e.g. Olins (2000) and Smith (1995) can be expanded, by implementing more experimental methods presented by e.g. Bernstein (1995), Dumaas (1994), Karjalainen (2001) and McGrory (2004). To explore whether and how companies may implement multiple sensory elements in their brand-building activities, we executed a case study in November and December 2005. Due to time-limitations we made a choice to restrict the scope of senses to be explored to the haptic sense, in addition to the visual. The target of the analysis was the Norwegian dairy producer TINE. To find suitable haptic qualities for the company, we carried out a workshop and further test at the Department of Product Design at the Norwegian University of Science and Technology. Chosen haptic specimens were subsequently implemented in what we call experimental haptic metaphors. Through tactile, kinetic and visual traits these metaphors, taking the form of clothing articles, were meant to express TINE’s identity in a new and clever way. For a company, explicit sensory metaphors may be used as means to express identity-aspects in untraditional ways. They can work as inspiration for sensory stimuli in the concrete manifestations of the company. Moreover they will provide the company with a tool for communication and exploration around identity aspects internally

Combining 3-D geovisualization with force feedback driven user interaction

We describe a prototype software system for investigating novel human-computer interaction techniques for 3-D geospatial data. This system, M4-Geo (Multi-Modal Mesh Manipulation of Geospatial data), aims to provide a more intuitive interface for directly manipulating 3-D surface data, such as digital terrain models (DTM). The M4-Geo system takes place within a 3-D environment and uses a Phantom haptic force feedback device to enhance 3-D computer graphics with touch-based interactions. The Phantom uses a 3-D force feedback stylus, which acts as a virtual “finger tip ” that allows the user to feel the shape (morphology) of the terrain’s surface in great detail. In addition, it acts as a touch sensitive tool for different GIS tasks, such as digitizing (draping) of lines and polygons directly onto a 3-D surface and directly deforming surfaces (by pushing or pulling the stylus in or out). The user may adjust the properties of the surface deformation (e.g., soft or hard) locally by painting it with a special “material color.” The overlap of visual and force representation of 3-D data aides hand-eye coordination for these tasks and helps the user to perceive the 3-D spatial data in a more holistic, multi-sensory way. The use of such a 3-D force feedback device for direct interaction may thus provide more intuitive and efficient alternatives to the mouse and keyboards driven interactions common today, in particular in areas related to digital landscape design, surface hydrology and geotechnical engineering

Tactility Trialing: Exploring Materials to Inform Tactile Experience Design

Although materials of tangible interaction designs largely determine their user experience, material choices are often steered by practical motives. This paper presents ‘tactility trialing’, an approach to explore tactile experiences of materials to inform the design of tangible artifacts. Through experience formulation, material selection, artifact creation and short user studies, designers and design-researchers are enabled to make informed decisions on the materials to be used in order to evoke the intended experience. The approach is illustrated through two case studies of student work. Tactility trialing helped them in getting acquainted with tactile material qualities in practice, and with the applicability of material characteristics such as resilience and hardness in design

Curve and surface framing for scientific visualization and domain dependent navigation

Thesis (Ph.D.) - Indiana University, Computer Science, 1996Curves and surfaces are two of the most fundamental types of objects in computer graphics. Most existing systems use only the 3D positions of the curves and surfaces, and the 3D normal directions of the surfaces, in the visualization process. In this dissertation, we attach moving coordinate frames to curves and surfaces, and explore several applications of these frames in computer graphics and scientific visualization. Curves in space are difficult to perceive and analyze, especially when they are densely clustered, as is typical in computational fluid dynamics and volume deformation applications. Coordinate frames are useful for exposing the similarities and differences between curves. They are also useful for constructing ribbons, tubes and smooth camera orientations along curves. In many 3D systems, users interactively move the camera around the objects with a mouse or other device. But all the camera control is done independently of the properties of the objects being viewed, as if the user is flying freely in space. This type of domain-independent navigation is frequently inappropriate in visualization applications and is sometimes quite difficult for the user to control. Another productive approach is to look at domain-specific constraints and thus to create a new class of navigation strategies. Based on attached frames on surfaces, we can constrain the camera gaze direction to be always parallel (or at a fixed angle) to the surface normal. Then users will get a feeling of driving on the object instead of flying through the space. The user's mental model of the environment being visualized can be greatly enhanced by the use of these constraints in the interactive interface. Many of our research ideas have been implemented in Mesh View, an interactive system for viewing and manipulating geometric objects. It contains a general purpose C++ library for nD geometry and supports a winged-edge based data structure. Dozens of examples of scientifically interesting surfaces have been constructed and included with the system

Digital Fabrication Approaches for the Design and Development of Shape-Changing Displays

Interactive shape-changing displays enable dynamic representations of data and information through physically reconfigurable geometry. The actuated physical deformations of these displays can be utilised in a wide range of new application areas, such as dynamic landscape and topographical modelling, architectural design, physical telepresence and object manipulation. Traditionally, shape-changing displays have a high development cost in mechanical complexity, technical skills and time/finances required for fabrication. There is still a limited number of robust shape-changing displays that go beyond one-off prototypes. Specifically, there is limited focus on low-cost/accessible design and development approaches involving digital fabrication (e.g. 3D printing). To address this challenge, this thesis presents accessible digital fabrication approaches that support the development of shape-changing displays with a range of application examples – such as physical terrain modelling and interior design artefacts. Both laser cutting and 3D printing methods have been explored to ensure generalisability and accessibility for a range of potential users. The first design-led content generation explorations show that novice users, from the general public, can successfully design and present their own application ideas using the physical animation features of the display. By engaging with domain experts in designing shape-changing content to represent data specific to their work domains the thesis was able to demonstrate the utility of shape-changing displays beyond novel systems and describe practical use-case scenarios and applications through rapid prototyping methods. This thesis then demonstrates new ways of designing and building shape-changing displays that goes beyond current implementation examples available (e.g. pin arrays and continuous surface shape-changing displays). To achieve this, the thesis demonstrates how laser cutting and 3D printing can be utilised to rapidly fabricate deformable surfaces for shape-changing displays with embedded electronics. This thesis is concluded with a discussion of research implications and future direction for this work

The cockpit for the 21st century

Interactive surfaces are a growing trend in many domains. As one possible manifestation of Mark Weiser’s vision of ubiquitous and disappearing computers in everywhere objects, we see touchsensitive screens in many kinds of devices, such as smartphones, tablet computers and interactive tabletops. More advanced concepts of these have been an active research topic for many years. This has also influenced automotive cockpit development: concept cars and recent market releases show integrated touchscreens, growing in size. To meet the increasing information and interaction needs, interactive surfaces offer context-dependent functionality in combination with a direct input paradigm. However, interfaces in the car need to be operable while driving. Distraction, especially visual distraction from the driving task, can lead to critical situations if the sum of attentional demand emerging from both primary and secondary task overextends the available resources. So far, a touchscreen requires a lot of visual attention since its flat surface does not provide any haptic feedback. There have been approaches to make direct touch interaction accessible while driving for simple tasks. Outside the automotive domain, for example in office environments, concepts for sophisticated handling of large displays have already been introduced. Moreover, technological advances lead to new characteristics for interactive surfaces by enabling arbitrary surface shapes. In cars, two main characteristics for upcoming interactive surfaces are largeness and shape. On the one hand, spatial extension is not only increasing through larger displays, but also by taking objects in the surrounding into account for interaction. On the other hand, the flatness inherent in current screens can be overcome by upcoming technologies, and interactive surfaces can therefore provide haptically distinguishable surfaces. This thesis describes the systematic exploration of large and shaped interactive surfaces and analyzes their potential for interaction while driving. Therefore, different prototypes for each characteristic have been developed and evaluated in test settings suitable for their maturity level. Those prototypes were used to obtain subjective user feedback and objective data, to investigate effects on driving and glance behavior as well as usability and user experience. As a contribution, this thesis provides an analysis of the development of interactive surfaces in the car. Two characteristics, largeness and shape, are identified that can improve the interaction compared to conventional touchscreens. The presented studies show that large interactive surfaces can provide new and improved ways of interaction both in driver-only and driver-passenger situations. Furthermore, studies indicate a positive effect on visual distraction when additional static haptic feedback is provided by shaped interactive surfaces. Overall, various, non-exclusively applicable, interaction concepts prove the potential of interactive surfaces for the use in automotive cockpits, which is expected to be beneficial also in further environments where visual attention needs to be focused on additional tasks.Der Einsatz von interaktiven Oberflächen weitet sich mehr und mehr auf die unterschiedlichsten Lebensbereiche aus. Damit sind sie eine mögliche Ausprägung von Mark Weisers Vision der allgegenwärtigen Computer, die aus unserer direkten Wahrnehmung verschwinden. Bei einer Vielzahl von technischen Geräten des täglichen Lebens, wie Smartphones, Tablets oder interaktiven Tischen, sind berührungsempfindliche Oberflächen bereits heute in Benutzung. Schon seit vielen Jahren arbeiten Forscher an einer Weiterentwicklung der Technik, um ihre Vorteile auch in anderen Bereichen, wie beispielsweise der Interaktion zwischen Mensch und Automobil, nutzbar zu machen. Und das mit Erfolg: Interaktive Benutzeroberflächen werden mittlerweile serienmäßig in vielen Fahrzeugen eingesetzt. Der Einbau von immer größeren, in das Cockpit integrierten Touchscreens in Konzeptfahrzeuge zeigt, dass sich diese Entwicklung weiter in vollem Gange befindet. Interaktive Oberflächen ermöglichen das flexible Anzeigen von kontextsensitiven Inhalten und machen eine direkte Interaktion mit den Bildschirminhalten möglich. Auf diese Weise erfüllen sie die sich wandelnden Informations- und Interaktionsbedürfnisse in besonderem Maße. Beim Einsatz von Bedienschnittstellen im Fahrzeug ist die gefahrlose Benutzbarkeit während der Fahrt von besonderer Bedeutung. Insbesondere visuelle Ablenkung von der Fahraufgabe kann zu kritischen Situationen führen, wenn Primär- und Sekundäraufgaben mehr als die insgesamt verfügbare Aufmerksamkeit des Fahrers beanspruchen. Herkömmliche Touchscreens stellen dem Fahrer bisher lediglich eine flache Oberfläche bereit, die keinerlei haptische Rückmeldung bietet, weshalb deren Bedienung besonders viel visuelle Aufmerksamkeit erfordert. Verschiedene Ansätze ermöglichen dem Fahrer, direkte Touchinteraktion für einfache Aufgaben während der Fahrt zu nutzen. Außerhalb der Automobilindustrie, zum Beispiel für Büroarbeitsplätze, wurden bereits verschiedene Konzepte für eine komplexere Bedienung großer Bildschirme vorgestellt. Darüber hinaus führt der technologische Fortschritt zu neuen möglichen Ausprägungen interaktiver Oberflächen und erlaubt, diese beliebig zu formen. Für die nächste Generation von interaktiven Oberflächen im Fahrzeug wird vor allem an der Modifikation der Kategorien Größe und Form gearbeitet. Die Bedienschnittstelle wird nicht nur durch größere Bildschirme erweitert, sondern auch dadurch, dass Objekte wie Dekorleisten in die Interaktion einbezogen werden können. Andererseits heben aktuelle Technologieentwicklungen die Restriktion auf flache Oberflächen auf, so dass Touchscreens künftig ertastbare Strukturen aufweisen können. Diese Dissertation beschreibt die systematische Untersuchung großer und nicht-flacher interaktiver Oberflächen und analysiert ihr Potential für die Interaktion während der Fahrt. Dazu wurden für jede Charakteristik verschiedene Prototypen entwickelt und in Testumgebungen entsprechend ihres Reifegrads evaluiert. Auf diese Weise konnten subjektives Nutzerfeedback und objektive Daten erhoben, und die Effekte auf Fahr- und Blickverhalten sowie Nutzbarkeit untersucht werden. Diese Dissertation leistet den Beitrag einer Analyse der Entwicklung von interaktiven Oberflächen im Automobilbereich. Weiterhin werden die Aspekte Größe und Form untersucht, um mit ihrer Hilfe die Interaktion im Vergleich zu herkömmlichen Touchscreens zu verbessern. Die durchgeführten Studien belegen, dass große Flächen neue und verbesserte Bedienmöglichkeiten bieten können. Außerdem zeigt sich ein positiver Effekt auf die visuelle Ablenkung, wenn zusätzliches statisches, haptisches Feedback durch nicht-flache Oberflächen bereitgestellt wird. Zusammenfassend zeigen verschiedene, untereinander kombinierbare Interaktionskonzepte das Potential interaktiver Oberflächen für den automotiven Einsatz. Zudem können die Ergebnisse auch in anderen Bereichen Anwendung finden, in denen visuelle Aufmerksamkeit für andere Aufgaben benötigt wird

Ubiquitous computing and natural interfaces for environmental information

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do Grau de Mestre em Engenharia do Ambiente, perfil Gestão e Sistemas AmbientaisThe next computing revolution‘s objective is to embed every street, building, room and object with computational power. Ubiquitous computing (ubicomp) will allow every object to receive and transmit information, sense its surroundings and act accordingly, be located from anywhere in the world, connect every person. Everyone will have the possibility to access information, despite their age, computer knowledge, literacy or physical impairment. It will impact the world in a profound way, empowering mankind, improving the environment, but will also create new challenges that our society, economy, health and global environment will have to overcome. Negative impacts have to be identified and dealt with in advance. Despite these concerns, environmental studies have been mostly absent from discussions on the new paradigm. This thesis seeks to examine ubiquitous computing, its technological emergence, raise awareness towards future impacts and explore the design of new interfaces and rich interaction modes. Environmental information is approached as an area which may greatly benefit from ubicomp as a way to gather, treat and disseminate it, simultaneously complying with the Aarhus convention. In an educational context, new media are poised to revolutionize the way we perceive, learn and interact with environmental information. cUbiq is presented as a natural interface to access that information