Fitting 3D morphable models using implicit representations

We consider the problem of approximating the 3D scan of a real object through an affine combination of examples. Common approaches depend either on the explicit estimation of point-to-point correspondences or on 2-dimensional projections of the target mesh; both present drawbacks. We follow an approach similar to [IF03] by representing the target via an implicit function, whose values at the vertices of the approximation are used to define a robust cost function. The problem is approached in two steps, by approximating first a coarse implicit representation of the whole target, and then finer, local ones; the local approximations are then merged together with a Poisson-based method. We report the results of applying our method on a subset of 3D scans from the Face Recognition Grand Challenge v.1.0.

Lag Camera: A Moving Multi-Camera Array for Scene-Acquisition

Many applications, such as telepresence, virtual reality, and interactive walkthroughs, require a three-dimensional(3D)model of real-world environments. Methods, such as lightfields, geometric reconstruction and computer vision use cameras to acquire visual samples of the environment and construct a model. Unfortunately, obtaining models of real-world locations is a challenging task. In particular, important environments are often actively in use, containing moving objects, such as people entering and leaving the scene. The methods previously listed have difficulty in capturing the color and structure of the environment while in the presence of moving and temporary occluders. We describe a class of cameras called lag cameras. The main concept is to generalize a camera to take samples over space and time. Such a camera, can easily and interactively detect moving objects while continuously moving through the environment. Moreover, since both the lag camera and occluder are moving, the scene behind the occluder is captured by the lag camera even from viewpoints where the occluder lies in between the lag camera and the hidden scene. We demonstrate an implementation of a lag camera, complete with analysis and captured environments.

Interactive Augmentation of Live Images using a HDR Stereo Camera

Adding virtual objects to real environments plays an important role in todays computer graphics: Typical examples are virtual furniture in a real room and virtual characters in real movies. For a believable appearance, consistent lighting of the virtual objects is required. We present an augmented reality system that displays virtual objects with consistent illumination and shadows in the image of a simple webcam. We use two high dynamic range video cameras with fisheye lenses permanently recording the environment illumination. A sampling algorithm selects a few bright parts in one of the wide angle images and the corresponding points in the second camera image. The 3D position can then be calculated using epipolar geometry. Finally, the selected point lights are used in a multi pass algorithm to draw the virtual object with shadows. To validate our approach, we compare the appearance and shadows of the synthetic objects with real objects.

Rendering Falling Leaves on Graphics Hardware

There is a growing interest in simulating natural phenomena in computer graphics applications. Animating natural scenes in real time is one of the most challenging problems due to the inherent complexity of their structure, formed by millions of geometric entities, and the interactions that happen within. An example of natural scenario that is needed for games or simulation programs are forests. Forests are difficult to render because the huge amount of geometric entities and the large amount of detail to be represented. Moreover, the interactions between the objects (grass, leaves) and external forces such as wind are complex to model. In this paper we concentrate in the rendering of falling leaves at low cost. We present a technique that exploits graphics hardware in order to render thousands of leaves with different falling paths in real time and low memory requirements.

Methods and Applications in Interactive Broadcasting

Interactive TV technology has been addressed in many previous works, but there is sparse research on the topic of interactive content broadcasting and how to support the production process. In this article, the interactive broadcasting process is broadly defined to include studio technology and digital TV applications at consumer set-top boxes. In particular, augmented reality studio technology employs smart-projectors as light sources and blends real scenes with interactive computer graphics that are controlled at end-user terminals. Moreover, TV producer-friendly multimedia authoring tools empower the development of novel TV formats. Finally, the support for user-contributed content raises the potential to revolutionize the hierarchical TV production process, by introducing the viewer as part of content delivery chain.

View-Dependent Extraction of Contours with Distance Transforms for Adaptive Polygonal for adaptive polygonal Mesh-Simplification

During decades Distance Transforms have proven to be useful for many image processing applications, and more recently, they have started to be used in computer graphics environments. The goal of this paper is to propose a new technique based on Distance Transforms for detecting mesh elements which are close to the objects' external contour (from a given point of view), and using this information for weighting the approximation error which will be tolerated during the mesh simplification process. The obtained results are evaluated in two ways: visually and using an objective metric that measures the geometrical difference between two polygonal meshes.

MHP Oriented Interactive Augmented Reality System for Sports Broadcasting Environments

Television and movie images have been altered ever since it was technically possible. Nowadays embedding advertisements, or incorporating text and graphics in TV scenes, are common practice, but they can not be considered as integrated part of the scene. The introduction of new services for interactive augmented television is discussed in this paper. We analyse the main aspects related with the whole chain of augmented reality production. Interactivity is one of the most important added values of the digital television: This paper aims to break the model where all TV viewers receive the same final image. Thus, we introduce and discuss the new concept of interactive augmented television, i. e. real time composition of video and computer graphics - e.g. a real scene and freely selectable images or spatial rendered objects - edited and customized by the end user within the context of the user's set top box and TV receiver.

Adaptive Cube Tessellation for Topologically Correct Isosurfaces

Three dimensional datasets representing scalar fields are frequently rendered using isosurfaces. For datasets arranged as a cubic lattice, the marching cubes algorithm is the most used isosurface extraction method. However, the marching cubes algorithm produces some ambiguities which have been solved using different approaches that normally imply a more complex process. One of them is to tessellate the cubes into tetrahedra, and by using a similar method (marching tetrahedra), to build the isosurface. The main drawback of other tessellations is that they do not produce the same isosurface topologies as those generated by improved marching cubes algorithms. We propose an adaptive tessellation that, being independent of the isovalue, preserves the topology. Moreover the tessellationallows the isosurface to evolve continuously when the isovalue is changed continuously.

GPU-based Ray Tracing of Dynamic Scenes

Interactive ray tracing of non-trivial scenes is just becoming feasible on single graphics processing units (GPU). Recent work in this area focuses on building effective acceleration structures, which work well under the constraints of current GPUs. Most approaches are targeted at static scenes and only allow navigation in the virtual scene. So far support for dynamic scenes has not been considered for GPU implementations. We have developed a GPU-based ray tracing system for dynamic scenes consisting of a set of individual objects. Each object may independently move around, but its geometry and topology are static.

Evaluation of Binocular Eye Trackers and Algorithms for 3D Gaze Interaction in Virtual Reality Environments

Tracking user’s visual attention is a fundamental aspect in novel human-computer interaction paradigms found in Virtual Reality. For example, multimodal interfaces or dialogue-based communications with virtual and real agents greatly benefit from the analysis of the user’s visual attention as a vital source for deictic references or turn-taking signals. Current approaches to determine visual attention rely primarily on monocular eye trackers. Hence they are restricted to the interpretation of two-dimensional fixations relative to a defined area of projection. The study presented in this article compares precision, accuracy and application performance of two binocular eye tracking devices. Two algorithms are compared which derive depth information as required for visual attention-based 3D interfaces. This information is further applied to an improved VR selection task in which a binocular eye tracker and an adaptive neural network algorithm is used during the disambiguation of partly occluded objects.

Efficient Bimanual Symmetric 3D Manipulation for Bare-Handed Interaction

Recently, stable markerless 6 DOF video based handtracking devices became available. These devices simultaneously track the positions and orientations of both user hands in different postures with at least 25 frames per second. Such hand-tracking allows for using the human hands as natural input devices. However, the absence of physical buttons for performing click actions and state changes poses severe challenges in designing an efficient and easy to use 3D interface on top of such a device. In particular, for coupling and decoupling a virtual object’s movements to the user’s hand (i.e. grabbing and releasing) a solution has to be found. In this paper, we introduce a novel technique for efficient two-handed grabbing and releasing objects and intuitively manipulating them in the virtual space. This technique is integrated in a novel 3D interface for virtual manipulations. A user experiment shows the superior applicability of this new technique. Last but not least, we describe how this technique can be exploited in practice to improve interaction by integrating it with RTT DeltaGen, a professional CAD/CAS visualization and editing tool.

3D-Druck von Kunststoff-Medizinprodukten

Das Additive Manufacturing gewinnt im Bereich der Medizintechnik zur Herstellung von Prototypen bis hin zu Endprodukten zunehmend an Bedeutung. Ein großes Hemmnis stellen allerdings die relativ hohen Fertigungskosten dar. Hier bietet der verstärkte Einsatz der 3D-Drucktechnologie (3D Printing) ein erhebliches Potential zur Reduktion der Kosten. Aus dieser Motivation heraus wurde ein 3D-Druckverfahren zur Herstellung biokompatibler, sterilisierbarer Kunststoffmodelle entwickelt. Beim 3D-Druck-Verfahren handelt es sich um einen pulverbasierten Prozess zur schichtweisen Herstellung von Modellen direkt aus Computerdaten. Dabei werden dünne Schichten eines Pulvers auf eine Grundplatte aufgebracht, die dann durch gezielte Binderzugabe entsprechend des aktuellen Bauteilquerschnitts verfestigt werden. Ausgangsmaterial für diesen Prozess ist ein Granulatgemisch auf Basis von PMMA (Polymethylmethacrylat). Als Binderflüssigkeit wird ein Lösungsmittel eingesetzt. Die 3D gedruckten Modelle werden nach einer entsprechenden Trocknungszeit im Pulverbett entpackt und warmgelagert, um das Abdampfen des Lösungsmittels zu beschleunigen. Der Nachweis der Biokompatibilität der hergestellten Modelle erfolgte durch einen Test nach DIN EN ISO 10993-5. In Kooperation mit Anwendern wurden verschiedene Anwendungsbeispiele wie Bohrschablonen, Otoplastiken, Gebissmodelle und Modelle für die präoperative Planung realisiert und charakterisiert.

Advantages and pitfalls in computer assisted orthopedic surgery planning using rapid-prototyped guides

Durch die von Rapid Prototyping gebotenen Möglichkeiten können computergestützte 3D Operationsplanungen präzise in der Operation umgesetzt werden. An der Universitätsklinik Balgrist wurden in den letzten 3 Jahren nahezu 100 Patienten erfolgreich behandelt, deren Operation in 3D geplant und mit patienten-spezifischen Schablonen umgesetzt wurde. Wir beschreiben die Genauigkeit dieser Methode und berichten über die hierbei gesammelten Erfahrungen. Aufgrund der Flexibilität der Rapid Prototyping Technologie, gibt es nicht immer nur einen Weg wie eine 3D geplante Operation umgesetzt werden kann. Wir zeigen daher anhand von Fallbeispielen unterschiedliche Strategien auf und beschreiben deren Vor- und Nachteile. Ausserdem präsentieren wir die Weiterentwicklung der Methode zur Anwendung an kleinerer Anatomie wie Knochen des Handgelenkes oder der Finger.