Virtual Rear Projection: A Comparison Study of Projection Technologies for Large Interactive Displays

Rear projection of large-scale upright displays is often preferred over front projection because of the elimination of shadows that occlude the projected image. However, rear projection is not always a feasible option for space and cost reasons. Recent research suggests that many of the desirable features of rear projection, in particular shadow elimination, can be reproduced using new front projection techniques. We report on an empirical study to determine how two of these new projection techniques compare with traditional rear projection and front projection, with the hope of motivating the continued advance of improved virtual rear projection techniques

Real-time shadows in OpenGL caused by the presence of multiple light sources

U suvremenoj računalnoj grafici naglasak je na detaljima prizora, a uzimajući u obzir poboljšanja hardverskih svojstava, nije dopušteno raditi kompromise kada je riječ o stvarnosti scena. Svaki odraz, sjena, zaobljeni kut ili prozirnost mora biti doveden do savršenstva i prikazan u cilju da se scena koja se oslikava učini što realističnijom. U jednom od najšire rabljenih API-ja za renderiranje 3D objekata, OpenGL-u, ne postoji nešto poput knjižnice za dodavanje ovih pojava koje postoje u stvarnosti. Ako se razmatra mogućnost postojanja više izvora svjetlosti, renderiranje svih ovih detalja postaje pravi izazov. Cilj ovog rada je obezbjeđivanje metoda za generiranje sjene na efikasan način, za objekte često rabljene kao komponente složenih 3D objekata, u uvjetima prisutnosti više svjetlosnih izvora s mogućnošću kretanja.In modern computer graphics, the emphasis is on the details of the scene, and taking into account the improvements in hardware performances, it is not allowed to make compromises when it comes to the reality of scenes. Each reflection, shadow, rounded corner and transparency must be brought to perfection and presented in order to make a depicted scene more realistic. In one of the most widely used API for rendering 3D objects, OpenGL, there is nothing similar to a library for adding those phenomena that exist in reality. If the possibility of existence of multiple light sources is considered, rendering all these details becomes a real challenge. The aim of this paper is to provide a method for generating shadows in an efficient way, for the objects commonly used as components of complex 3D objects, in conditions of the presence of moving light sources

Synchronized Illumination Modulation for Digital Video Compositing

Informationsaustausch ist eines der Grundbedürfnisse der Menschen. Während früher dazu Wandmalereien,Handschrift, Buchdruck und Malerei eingesetzt wurden, begann man später, Bildfolgen zu erstellen, die als sogenanntes ”Daumenkino” den Eindruck einer Animation vermitteln. Diese wurden schnell durch den Einsatz rotierender Bildscheiben, auf denen mit Hilfe von Schlitzblenden, Spiegeln oder Optiken eine Animation sichtbar wurde, automatisiert – mit sogenannten Phenakistiskopen,Zoetropen oder Praxinoskopen. Mit der Erfindung der Fotografie begannen in der zweiten Hälfte des 19. Jahrhunderts die ersten Wissenschaftler wie Eadweard Muybridge, Etienne-Jules Marey und Ottomar Anschütz, Serienbildaufnahmen zu erstellen und diese dann in schneller Abfolge, als Film, abzuspielen. Mit dem Beginn der Filmproduktion wurden auch die ersten Versuche unternommen, mit Hilfe dieser neuen Technik spezielle visuelle Effekte zu generieren, um damit die Immersion der Bewegtbildproduktionen weiter zu erhöhen. Während diese Effekte in der analogen Phase der Filmproduktion bis in die achtziger Jahre des 20.Jahrhunderts recht beschränkt und sehr aufwendig mit einem enormen manuellen Arbeitsaufwand erzeugt werden mussten, gewannen sie mit der sich rapide beschleunigenden Entwicklung der Halbleitertechnologie und der daraus resultierenden vereinfachten digitalen Bearbeitung immer mehr an Bedeutung. Die enormen Möglichkeiten, die mit der verlustlosen Nachbearbeitung in Kombination mit fotorealistischen, dreidimensionalen Renderings entstanden, führten dazu, dass nahezu alle heute produzierten Filme eine Vielfalt an digitalen Videokompositionseffekten beinhalten. ...Besides home entertainment and business presentations, video projectors are powerful tools for modulating images spatially as well as temporally. The re-evolving need for stereoscopic displays increases the demand for low-latency projectors and recent advances in LED technology also offer high modulation frequencies. Combining such high-frequency illumination modules with synchronized, fast cameras, makes it possible to develop specialized high-speed illumination systems for visual effects production. In this thesis we present different systems for using spatially as well as temporally modulated illumination in combination with a synchronized camera to simplify the requirements of standard digital video composition techniques for film and television productions and to offer new possibilities for visual effects generation. After an overview of the basic terminology and a summary of related methods, we discuss and give examples of how modulated light can be applied to a scene recording context to enable a variety of effects which cannot be realized using standard methods, such as virtual studio technology or chroma keying. We propose using high-frequency, synchronized illumination which, in addition to providing illumination, is modulated in terms of intensity and wavelength to encode technical information for visual effects generation. This is carried out in such a way that the technical components do not influence the final composite and are also not visible to observers on the film set. Using this approach we present a real-time flash keying system for the generation of perspectively correct augmented composites by projecting imperceptible markers for optical camera tracking. Furthermore, we present a system which enables the generation of various digital video compositing effects outside of completely controlled studio environments, such as virtual studios. A third temporal keying system is presented that aims to overcome the constraints of traditional chroma keying in terms of color spill and color dependency. ..

Body image distortion in photography

This thesis investigates the theory that photography is, in terms of body image perception, an intrinsically distorting and often fattening medium. In the professional practice of photography, film and television, there is a widely held belief that the camera "adds 10lbs" to the portrayed weight of actors and presenters. The primary questions addressed here relate to the true extent of the fattening effect, to what perceptual mechanisms it can be ascribed and if it can be counteracted in common practice. Current theories in the perception of photographic images rarely, if ever discuss the medium's perceptual accuracy in recording the original scene. It is assumed by many users that most photographs convey essentially the same information they would have seen had they been present when they were taken. Further, it is generally accepted that photographs are an accurate, veridical and scientific method of record and their content should be trusted unless there is evidence of a technical failure, editing or deliberate tampering. This thesis investigates whether this level of trust is appropriate, specifically by examining the reliability of photography in relation to reproducing the face and form of human subjects. Body Image Distortion (B.I.D.) is a term normally used to describe the primary diagnostic symptom of the slimming disease, anorexia nervosa. However, it is demonstrated here that people viewing 2D photographic portraits often make very significant overestimations of size when comparing otherwise identical stereoscopic images. The conclusion is that losing stereoscopic information in conventional 2D photography will cause distortions of perceived body image, and that this is often seen as a distinct flattening and fattening effect. A second fattening effect was also identified in the use of telephoto lenses. It is demonstrated, using psychophysical experiments and geometry that these 2D images cannot convey the same spatial or volumetric information that normal human orthostereoscopic perception will give. The evidence gathered suggests that the Human Visual System requires images to be orthostereoscopic, and be captured using two cameras that mimic as closely as possible the natural vergences, angle of view, depth of field, magnification, brightness, contrast and colour to reproduce scenes as accurately as possible. The experiments reported use three different size estimation methodologies: stereoscopic versus monocular comparisons of human and virtual targets, bodyweight estimations in portraits taken at differing camera to subject distances and synoptic versus direct viewing comparisons. The three techniques were used because photographic images are typically made without disparity and accommodation/vergence information, but with magnifications that are greater than found with direct viewing of a target. By separately analysing the effects of disparity, magnification and accommodation/vergence the reported experiments show how changes in each condition can effect size estimation in photographs. The data suggest that photographs made without orthostereoscopic information will lead to predictably distorted perception and that conventional 2D imaging will almost always cause a significant flattening and fattening effect. In addition, it is argued that the conveyed jaw size, in relation to neck width is an important factor in body-weight perception and this will lead to sexually dimorphic perception: disproportionately larger estimations of bodyweight are made for female faces than male faces under the same photographic conditions

Dynamic surface completion : the joint formation of color, texture, and shape

Dynamic surface completion is a phenomenon of visual filling-in where a colored pattern perceptually spreads onto an area confined by virtual contours in a multi-aperture motion display. The spreading effect is qualitatively similar to static texture spreading but widely surpasses it in strength, making it particularly suited for quantitative studies of visual interpolation processes. I carried out six experiments to establish with objective tasks that homogeneous color, as well as non-uniform texture spreading is a genuine representation of surface qualities and thus goes beyond mere contour interpolation. The experiments also serve to relate the phenomena to ongoing discussions about potentially responsible mechanisms for spatiotemporal integration: With a phenomenological method, I examined to what extent simple sensory persistence might be causally involved in the effect under consideration. The findings are partially consistent with the idea of sensory persistence, and indicate that information fragments are integrated over a time window of about 100 to 150 ms to form a complete surface representation

A right hemisphere advantage for processing blurred faces

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Shadow Elimination and Occluder Light Suppression for Multi-Projector Displays

Two related problems of front projection displays which occur when users obscure a projector are: (i) undesirable shadows cast on the display by the users, and (ii) projected light falling on and distracting the users. This paper provides a computational framework for solving these two problems based on multiple overlapping projectors and cameras. The overlapping projectors are automatically aligned to display the same dekeystoned image. The system detects when and where shadows are cast by occluders and is able to determine the pixels which are occluded in different projectors. Through a feedback control loop, the contributions of unoccluded pixels from other projectors are boosted in the shadowed regions, thereby eliminating the shadows. In addition, pixels which are being occluded are blanked, thereby preventing the projected light from falling on a user when they occlude the display. This can be accomplished even when the occluders are not visible to the camera. The paper presents results from a number of experiments demonstrating that the system converges rapidly with low steady-state errors

Effekte und Potenziale eines gebogenen interaktiven Displays

Ein heutiger Computerarbeitsplatz besteht normalerweise aus einer horizontalen Arbeitsfläche und mindestens einem vertikalen Bildschirm. Beide Orientierungen der Arbeitsbereiche haben Vorteile für einzelne Arbeitsschritte. Auf vertikalen Flächen ist beispielsweise das Lesen langer Texte ergonomischer, während das direkte Bearbeiten von Texten auf horizontalen Flächen weniger anstrengend ist. Der Wechsel zwischen den beiden Arbeitsbereichen ist jedoch umständlich, da die horizontale Arbeitsfläche häufig nicht digital ist. Doch selbst die steigende Verbreitung berührungsempfindlicher Bildschirme im horizontalen Arbeitsbereich (z.B. Tablets) löst dieses Problem nicht. Zwar bringen diese Geräte zum einen die Vorteile direkter Interaktion mit sich, führen aber zum anderen zur Frage, wie die digitalen Inhalte zwischen den unterschiedlich orientierten, digitalen Bereichen ausgetauscht werden. Eine Lösung hierfür ist die Kombination unterschiedlich orientierter Displays. Es gibt mehrere Ansätze diese zu kombinieren, jedoch sind die Displays dabei meistens physikalisch voneinander getrennt. Das führt dazu, dass der Nutzer die Displays zum einen eher als separate Einheiten wahrnimmt und zum anderen kein einfacher Übergang zwischen den Displays möglich ist. Eine Verbindungsart, die bis jetzt noch weitgehend unerforscht ist, ist die Kombination beider Displaybereiche durch eine gebogene Verbindung. Die Biegung stellt eine nahtlose Verbindung und einen unterbrechungsfreien Übergang zwischen den Displaybereichen her. Der Effekt eines solchen Übergangs auf die Nutzerinteraktion ist jedoch unbekannt. Die Biegung des Bildschirms eröffnet darüber hinaus auch die Möglichkeit für neuartige Visualisierungen, die von der nahtlosen Kombination unterschiedlicher Displayorientierungen profitieren. Außerdem können auch gewöhnliche, grafische Benutzerschnittstellen hinsichtlich der Displayform optimiert werden. Im Rahmen dieser Arbeit wird ein solches Display vorgestellt und dessen Effekte auf die Nutzerinteraktion und Potenziale für grafische Benutzerschnittstellen untersucht. Der Curve ist ein interaktives Display, das einen horizontalen und einen vertikalen Bereich durch eine nahtlose, gebogene Verbindung kombiniert. Im ersten Teil der Arbeit werden die Entwicklung der Displayform und die technische Umsetzung des Prototyps beschrieben. Anschließend wird im zweiten Teil der Einfluss der Displayform sowohl auf direkte als auch auf indirekte Interaktionsarten evaluiert. Außerdem wird der Curve um eine greifbare Benutzerschnittstelle erweitert und die Auswirkung der Displayform auf die Bedienbarkeit dieser Schnittstelle untersucht. Im dritten Teil werden zwei Visualisierungen und eine vorhandene, grafische Benutzerschnittstelle vorgestellt, die jeweils an die gebogene Displayform angepasst wurden. Die praktischen Erfahrungen aus den Entwicklungsprozessen werden dann in Form von Empfehlungen für vergleichbare Displayprojekte zusammengefasst. Am Ende der Arbeit stehen sowohl Ausgangspunkte für eine technische Weiterentwicklung, als auch weitere exemplarische Anwendungsszenarien, die von der gebogenen Displayform des Curve profitieren können.The working environment in a current office usually consists of a horizontal working area and at least one vertical digital display. Both workspace orientations offer specific advantages for a certain task. While reading a long documentis easier on a vertical display, editing a document is less exhausting on a horizontal working area. If a user wants to benefit from these advantages the working area has to be changed frequently, which is time-consuming as most of today’s horizontal areas are non-digital. This problem even remains as more and more interactive displays (e.g. tablets) are used on the horizontal surface because the content cannot be seamlessly transferred between them. Although these interactive horizontal displays offer direct interaction with digital content, transferring digital content between both display orientations is cumbersome. A solution for this problem is the combination of differently oriented working areas. There are different ways of combining display areas. Most of them still rely on physically separated displays. This hampers the transfer of documents from one display area to the other. The user also perceives the displays as separated areas. Another way, which could overcome these problems is a curved display connection. While the curved connection allows for a seamless transition between differently oriented display areas, it remains unclear how it simultaneously influences the interaction of the user. Besides this influence on the interaction a curved connection also allows for new ways of visualizing data using both display orientations in a single visualization or an adapted graphical user interface. This thesis presents an approach towards a curved connection of differently oriented display areas. The Curve is an interactive display that seamlessly combines a horizontal display area and a vertically inclined display area with a curved connection. The first part of this work presents the fundamental design of the Curve and its technical implementation in terms of hard- and software. Based on the constructed prototype several studies about the Curve’s influence on basic interaction techniques were conducted and are described in the second part of this thesis. These studies include direct interaction as well as indirect input using a pointing device and a first exploration of a graspable user interface. The next part describes the development of novel visualizations and a graphical user interface, which rely on the Curve’s display form. Lessons learned from these projects led to a first draft of guidelines for the development of similar displays and interfaces, which conclude the third part of this thesis. The last part summarizes the entire thesis and points at possible future steps like the technical improvement of the Curve’s technology and further application scenarios, which might also benefit from a curved display environment