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Wientapper, Folker; Schmitt, Michael; Fraissinet-Tachet, Matthieu; Kuijper, Arjan

A Universal, Closed-form Approach for Absolute Pose Problems

2018

Computer Vision and Image Understanding

We propose a general approach for absolute pose problems including the well known perspective-n-point (PnP) problem, its generalized variant (GPnP) with and without scale, and the pose from 2D line correspondences (PnL). These have received a tremendous attention in the computer vision community during the last decades. However, it was only recently that efficient, globally optimal, closed-form solutions have been proposed, which can handle arbitrary numbers of correspondences including minimal configurations as well as over-constrained cases with linear complexity. We follow the general scheme by eliminating the linear parameters first, which results in a least squares error function that only depends on the non-linear rotation and a small symmetric coefficient matrix of fixed size. Then, in a second step the rotation is solved with algorithms which are derived using methods from algebraic geometry such as the Gröbner basis method. We propose a unified formulation based on a representation with orthogonal complements which allows to combine different types of constraints elegantly in one single framework. We show that with our unified formulation existing polynomial solvers can be interchangeably applied to problem instances other than those they were originally proposed for. It becomes possible to compare them on various registrations problems with respect to accuracy, numerical stability, and computational speed. Our compression procedure not only preserves linear complexity, it is even faster than previous formulations. For the second step we also derive an own algebraic equation solver, which can additionally handle the registration from 3D point-to-point correspondences, where other rotation solvers fail. Finally, we also present a marker-based SLAM approach with automatic registration to a target coordinate system based on partial and distributed reference information. It represents an application example that goes beyond classical camera pose estimation from image measurements and also serves for evaluation on real data.

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Wientapper, Folker; Kuijper, Arjan

Unifying Algebraic Solvers for Scaled Euclidean Registration from Point, Line and Plane Constraints

2017

Computer Vision - ACCV 2016. Part V

Asian Conference on Computer Vision (ACCV) <13, 2016, Taipei, Taiwan>

We investigate recent state-of-the-art algorithms for absolute pose problems (PnP and GPnP) and analyse their applicability to a more general type, namely the scaled Euclidean registration from pointto- point, point-to-line and point-to plane correspondences. Similar to previous formulations we first compress the original set of equations to a least squares error function that only depends on the non-linear rotation parameters and a small symmetric coefficient matrix of fixed size. Then, in a second step the rotation is solved with algorithms which are derived using methods from algebraic geometry such as the Gröbner basis method. In previous approaches the first compression step was usually tailored to a specific correspondence types and problem instances. Here, we propose a unified formulation based on a representation with orthogonal complements which allows to combine different types of constraints elegantly in one single framework. We show that with our unified formulation existing polynomial solvers can be interchangeably applied to problem instances other than those they were originally proposed for. It becomes possible to compare them on various registrations problems with respect to accuracy, numerical stability, and computational speed. Our compression procedure not only preserves linear complexity, it is even faster than previous formulations. For the second step we also derive an own algebraic equation solver, which can additionally handle the registration from 3D point-to-point correspondences, where other solvers surprisingly fail.

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Wientapper, Folker; Wuest, Harald; Becker, Mario; Engelke, Timo; Haske, Leon; Bockholt, Ulrich

Initialisierung des Trackings mit Hilfe von Machine-Learning-Verfahren

2016

Angewandte Virtuelle Techniken im Produktentstehungsprozess

Kap. 5 beschreibt die Forschungsthemen zum Schwerpunkt Tracking. Darunter ist das Erfassen der Position und Orientierung von Objekten bzw. des Anwenders im dreidimensionalen Raum zu verstehen. Die Arbeiten bilden damit die Grundlage für darauf aufbauende Funktionen wie beispielsweise die lagekorrekte Einblendung zusätzlicher Informationen oder die intuitive Interaktion durch Gesten. Neben Ansätzen zur Weiterentwicklung der Algorithmen des markerlosen Trackings werden ergänzende Sensoriken wie Wegaufnehmer an Robotern, Inertialsensoriken an Kameras betrachtet. Ein weiterer Ansatz untersucht die Hinzunahme von CAD-Daten zur Verbesserung des bildbasierten Trackings.

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Wientapper, Folker; Wuest, Harald; Becker, Mario; Engelke, Timo; Haske, Leon; Bockholt, Ulrich

Online Learning Verfahren für markerloses Tracking

2016

Angewandte Virtuelle Techniken im Produktentstehungsprozess

Kap. 5 beschreibt die Forschungsthemen zum Schwerpunkt Tracking. Darunter ist das Erfassen der Position und Orientierung von Objekten bzw. des Anwenders im dreidimensionalen Raum zu verstehen. Die Arbeiten bilden damit die Grundlage für darauf aufbauende Funktionen wie beispielsweise die lagekorrekte Einblendung zusätzlicher Informationen oder die intuitive Interaktion durch Gesten. Neben Ansätzen zur Weiterentwicklung der Algorithmen des markerlosen Trackings werden ergänzende Sensoriken wie Wegaufnehmer an Robotern, Inertialsensoriken an Kameras betrachtet. Ein weiterer Ansatz untersucht die Hinzunahme von CAD-Daten zur Verbesserung des bildbasierten Trackings.

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Wientapper, Folker; Wuest, Harald; Becker, Mario; Engelke, Timo; Haske, Leon; Bockholt, Ulrich

Sensorfusion zur Realisierung hybrider Trackingverfahren

2016

Angewandte Virtuelle Techniken im Produktentstehungsprozess

Kap. 5 beschreibt die Forschungsthemen zum Schwerpunkt Tracking. Darunter ist das Erfassen der Position und Orientierung von Objekten bzw. des Anwenders im dreidimensionalen Raum zu verstehen. Die Arbeiten bilden damit die Grundlage für darauf aufbauende Funktionen wie beispielsweise die lagekorrekte Einblendung zusätzlicher Informationen oder die intuitive Interaktion durch Gesten. Neben Ansätzen zur Weiterentwicklung der Algorithmen des markerlosen Trackings werden ergänzende Sensoriken wie Wegaufnehmer an Robotern, Inertialsensoriken an Kameras betrachtet. Ein weiterer Ansatz untersucht die Hinzunahme von CAD-Daten zur Verbesserung des bildbasierten Trackings.

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Engelke, Timo; Keil, Jens; Rojtberg, Pavel; Wientapper, Folker; Schmitt, Michael; Bockholt, Ulrich

Content First - A concept for Industrial Augmented Reality Maintenance Applications using Mobile Devices

2015

MMSys '15

Multimedia Systems Conference (MMSys) <6, 2015, Portland, OR, USA>

Although AR has a long history in the area of maintenance and service-support in industry, there still is a lack of lightweight, yet practical solutions for handheld AR systems in everyday workflows. Attempts to support complex maintenance tasks with AR still miss reliable tracking techniques, simple ways to be integrated into existing maintenance environments, and practical authoring solutions, which minimize costs for specialized content generation. We present a general, customisable application framework, allowing to employ AR and VR techniques in order to support technicians in their daily tasks. In contrast to other systems, we do not aim to replace existing support systems such as traditional manuals. Instead we integrate well-known AR- and novel presentation techniques with existing instruction media. To this end practical authoring solutions are crucial and hence we present an application development system based on web-standards such as HTML,CSS and X3D.

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Wientapper, Folker; Engelke, Timo; Keil, Jens; Wuest, Harald; Mensik, Johanna

User Friedly Calibration and Tracking for Optical Stereo See-Through Augmented Reality

2014

IEEE International Symposium on Mixed and Augmented Reality - Science & Technology 2014

IEEE International Symposium on Mixed and Augmented Reality (ISMAR) <13, 2014, Munich, Germany>

Optical see through head mounted displays (OST-HMD) are ever since the first days of Augmented Reality (AR) in focus of development and in nowadays first affordable and prototypes are spread out to markets. Despite common technical problems, such as having a proper field of view, weight, and other problems concerning the miniaturization of these systems, a crucial aspect for AR relies also in the calibration of such a device with respect to the individual user for proper alignment of augmentations. Our demonstrator shows a practical solution for this problem along with a fully featured example application for a typical maintenance use case based on a generalized framework for application creation. We depict the technical background and procedure of the calibration, the tracking approach considering the sensors of the device, user experience factors, and its implementation procedure in general. We present our demonstrator using an Epson Moverio BT-200 OST-HMD.

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Wientapper, Folker; Wuest, Harald; Rojtberg, Pavel; Fellner, Dieter W.

A Camera-Based Calibration for Automotive Augmented Reality Head-Up-Displays

2013

12th IEEE International Symposium on Mixed and Augmented Reality 2013.

IEEE International Symposium on Mixed and Augmented Reality (ISMAR) <12, 2013, Adelaide, SA, Australia>

Using Head-up-Displays (HUD) for Augmented Reality requires to have an accurate internal model of the image generation process, so that 3D content can be visualized perspectively correct from the viewpoint of the user. We present a generic and cost-effective camera-based calibration for an automotive HUD which uses the windshield as a combiner. Our proposed calibration model encompasses the view-independent spatial geometry, i.e. the exact location, orientation and scaling of the virtual plane, and a view-dependent image warping transformation for correcting the distortions caused by the optics and the irregularly curved windshield. View-dependency is achieved by extending the classical polynomial distortion model for cameras and projectors to a generic five-variate mapping with the head position of the viewer as additional input. The calibration involves the capturing of an image sequence from varying viewpoints, while displaying a known target pattern on the HUD. The accurate registration of the camera path is retrieved with state-of-the-art vision-based tracking. As all necessary data is acquired directly from the images, no external tracking equipment needs to be installed. After calibration, the HUD can be used together with a head-tracker to form a head-coupled display which ensures a perspectively correct rendering of any 3D object in vehicle coordinates from a large range of possible viewpoints. We evaluate the accuracy of our model quantitatively and qualitatively.

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Bockholt, Ulrich; Wuest, Harald; Wientapper, Folker; Engelke, Timo; Webel, Sabine

Augmented Reality Assistenzsysteme für Wartung und Service in Industrie, Bau und Gebäudemanagement

2013

16. IFF-Wissenschaftstage 2013. Tagungsband

IFF-Wissenschaftstage <16, 2013, Magdeburg, Germany>

Für die Nutzbarkeit von Augmented Reality ist die Voraussetzung entscheidend, dass sich der Einsatz von AR im industriellen Kontext insbesondere dann rentiert, wenn sich Skaleneffekte einstellen. Im Bereich von Montage-, Reparatur- und Fehlerdiagnosearbeiten ist dies der Fall, wenn einerseits ein und dieselbe AR-Applikation in hohem Maße mehrfach benutzt werden kann, und andererseits die Erstellung des Trackingmodells hierfür nur einmal durchgeführt werden muss. Mit der Häufigkeit der Anwendung amortisiert sich dann der Aufwand für das einmalige Einrichten der AR-Applikation. Weiterhin ist es für die Akzeptanz von AR-Applikationen vorteilhaft, wenn beim Endanwender keine besonderen Kenntnisse hinsichtlich des Trackings bzw. der Benutzung der AR-Applikation vorausgesetzt werden müssen. Die AR-Applikation sollte den Endanwender bei der Erreichung seiner persönlichen Arbeitsziele unterstützen, ihm jedoch nicht ein zu hohes Maß an zusätzlichem Vorwissen in der Handhabung abverlangen. Seine Aufmerksamkeit sollte nicht darauf ausgerichtet sein, wie er sich verhalten muss, damit das Tracking funktioniert. Vielmehr muss er durch AR schneller, einfacher und intuitiver an die benötigten Informationen gelangen.

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Bockholt, Ulrich; Wientapper, Folker; Wuest, Harald; Fellner, Dieter W.

Augmented-Reality-basierte Interaktion mit Smartphone-Systemen zur Unterstützung von Servicetechnikern

2013

at - Automatisierungstechnik

Smartphonesysteme erfordern neue Interaktionsparadigmen, die die integrierte Sensorik auswerten (GPS, Inertial, Kompass), die aber insbesondere auf die Smartphonekamera aufsetzten, mit der die Umgebung aufgezeichnet wird. In diesem Zusammenhang liefern Augmented Reality Verfahren großes Potential besonders für industrielle Anwendung bei Wartungs- und Instandsetzungsarbeiten.

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Engelke, Timo; Keil, Jens; Rojtberg, Pavel; Wientapper, Folker; Webel, Sabine; Bockholt, Ulrich

Content First - A concept for Industrial Augmented Reality Maintenance Applications Using Mobile Devices

2013

12th IEEE International Symposium on Mixed and Augmented Reality 2013.

IEEE International Symposium on Mixed and Augmented Reality (ISMAR) <12, 2013, Adelaide, SA, Australia>

Although AR has a long history in the area of maintenance and service-support in industry, there still is a lack of lightweight, yet practical solutions for handheld AR systems in everyday workflows. Attempts to support complex maintenance tasks with AR still miss reliable tracking techniques, simple ways to be integrated into existing maintenance environments, and practical authoring solutions, which minimize costs for specialized content generation. We present a general, customisable application framework, allowing to employ AR and VR techniques in order to support technicians in their daily tasks. In contrast to other systems, we do not aim to replace existing support systems such as traditional manuals. Instead we integrate well-known AR- and novel presentation techniques with existing instruction media. To this end practical authoring solutions are crucial and hence we present an application development system based on web-standards such as HTML,CSS and X3D.

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Keil, Jens; Zöllner, Michael; Engelke, Timo; Wientapper, Folker; Schmitt, Michael

Controlling and Filtering Information Density with Spatial Interaction Techniques via Handheld Augmented Reality

2013

Virtual Augmented and Mixed Reality. Designing and Developing Augmented and Virtual Environments. Proceedings Part I

International Conference Virtual Augmented and Mixed Reality (VAMR) <5, 2013, Las Vegas, NV, USA>

In our paper we are proposing a method for contextual information filtering based on the user's movement and location in order to enable the intuitive usage of an "internet of things" via augmented reality (AR) without information overload. Similar to Ray & Charles Eames' "Power of Ten" and Jef Raskin's "Zooming Interface" we are displaying seamless information layers by simply moving around a Greek statue or a miniature model of an Ariane-5 space rocket. Therefore we are employing concepts of camera- and motion-based interaction techniques and use the metaphors of "investigation" and "exploration" to control the way augmented and visually superimposed elements are presented in order to mediate information in an enhanced and engaging manner with aspects of digital storytelling techniques.

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Amoretti, Michele; Copelli, Sergio; Wientapper, Folker; Furfari, Francesco; Lenzi, Stefano; Chessa, Stefano

Sensor Data Fusion for Activity Monitoring in the PERSONA Ambient Assisted Living Project

2013

Journal of Ambient Intelligence and Humanized Computing

User activity monitoring is a major problem in ambient assisted living, since it requires to infer new knowledge from collected and fused sensor data while dealing with highly dynamic environments, where devices continuously change their availability and (or) physical location. In the context of the European project PERSONA, we have developed an activity monitoring sub-system characterized by high modularity, little invasiveness of the environment and good responsiveness. In this paper we first illustrate the functional architecture of the proposed solution from a general point of view, discussing the motivations of the design. Then we describe in details the software components- sensor abstraction and integration layer, human posture classification, activity monitor-and the resulting activity monitoring application, presenting also a performance evaluation.

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Wientapper, Folker; Wuest, Harald; Kuijper, Arjan

Composing the Feature Map Retrieval Process for Robust and Ready-to-Use Monocular Tracking

2011

Computers & Graphics

This paper focuses on the preparative process of natural feature map retrieval for a mobile camera-based tracking system. We cover the most important aspects of a general purpose tracking system including the acquisition of the scene's geometry, tracking initialization and fast and accurate frame-by-frame tracking. To this end, several state-of-the-art techniques - each targeted at one particular subproblem - are fused together, whereby their interplay and complementary benefits form the core of the system and the thread of our discussion. The choice of the individual sub-algorithms in our system reflects the scarcity of computational resources on mobile devices. In order to allow a more accurate, more robust and faster tracking during run-time, we therefore transfer the computational load into the preparative customization step wherever possible. From the viewpoint of the user, the preparative stage is kept very simple. It only involves recording the scene from various viewpoints and defining a transformation into a target coordinate frame via manual definition of only a few 3D to 3D point correspondences. Technically, the image sequence is used to (1) capture the scene's geometry by a SLAM-Method and subsequent refinement via constrained Bundle Adjustment, (2) to train a Randomized-Trees classifier for wide-baseline tracking initialization, and (3) to analyze the view-point dependent visibility of each feature. During run-time, robustness and performance of the frame-to-frame tracking are further increased by fusing inertial measurements within a combined pose estimation.

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Ahrens, Katrin; Wientapper, Folker [Betreuer]

Feature-Basiertes Tracking mittels Bag Of Visual Words

2011

Darmstadt, FH, Master Thesis, 2011

Motivation dieser Arbeit ist die Entwicklung eines Programms zur Unterstützung von Monteuren bei der Wartung und Reparatur eines Fahrzeugs. Durch automatische Einblendungen, welche in der erfassten Szene angezeigt werden, wird vorgegeben welcher Schritt als nächstes ausgeführt werden soll. Unter anderem sollen die zu bearbeitenden Stellen durch das Einblenden von CAD-Objekten hervorgehoben werden. Um die Objekte an der richtigen Stelle einzublenden, muss die aktuelle Position und Orientierung der Kamera bekannt sein. Zur Berechnung der Kamerapose ist ein zuverlässiges Feature-Matching nötig, bei dem die benötigte 3D-Position der Features bestimmt wird. Da das System in Echtzeit arbeiten soll, kommt es hierbei vor allem auf eine schnelle aber dennoch genaue Ausführung an. Eine vielversprechende Methode zur Verkürzung der benötigten Rechenzeit besteht in der Kombination von Matching mit Visual Words. Das Ziel dieser Arbeit ist daher die Entwicklung eines Systems zum Feature-Matching mit Hilfe der Visual Words und wird ergänzt durch die anschließende Berechnung der Kamerapose. Als Feature-Detektor wird der SURF-Algorithmus verwendet. Die Visual Words werden umgesetzt, indem in der Lernphase die Features aller Bilder in Cluster eingeteilt werden. In Histogrammen wird festgehalten, wie sich die Features eines Bildes auf die Cluster verteilen. Beim späteren Tracking wird anhand von aktuellen Features ein Histogramm erstellt und mit den gespeicherten Histogrammen verglichen. Für das Matching werden nur diejenigen Bilder ausgewählt, die ein ähnliches Histogramm besitzen. Dies führt zu einer besseren und vor allem schnelleren Auswahl der Features, da Features, welche in diesem Bildausschnitt nicht vorkommen können, von der Suche ausgeschlossen werden. Dieses Vorgehen ermöglicht ein schnelles und gleichzeitig genaues Matching, wodurch auch die Berechnung der Kamerapose beschleunigt wird. Während die berechnete Kamerapose für ein durchgängiges Tracking möglicherweise nicht stabil genug ist, bietet sich das Verfahren vor allem für eine schnelle Initialisierungsphase an.

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Wientapper, Folker; Wuest, Harald; Kuijper, Arjan

Reconstruction and Accurate Alignment of Feature Maps for Augmented Reality

2011

3DIMPVT 2011

International Conference on 3D Imaging, Modeling, Processing, Visualization and Transmission (3DIMPVT) <1, 2011, Hangzhou, China>

This paper focuses on the preparative process of retrieving accurate feature maps for a camera-based tracking system. With this system it is possible to create ready-touse Augmented Reality applications with a very easy setup work-flow, which in practice only involves three steps: filming the object or environment from various viewpoints, defining a transformation between the reconstructed map and the target coordinate frame based on a small number of 3D-3D correspondences and, finally, initiating a feature learning and Bundle Adjustment step. Technically, the solution comprises several sub-algorithms. Given the image sequence provided by the user, a feature map is initially reconstructed and incrementally extended using a Simultaneous-Localization-and-Mapping (SLAM) approach. For the automatic initialization of the SLAM module, a method for detecting the amount of translation is proposed. Since the initially reconstructed map is defined in an arbitrary coordinate system, we present a method for optimally aligning the feature map to the target coordinated frame of the augmentation models based on 3D-3D correspondences defined by the user. As an initial estimate we solve for a rigid transformation with scaling, known as Absolute Orientation. For refinement of the alignment we present a modification of the well-known Bundle Adjustment, where we include these 3D-3D-correspondences as constraints. Compared to ordinary Bundle Adjustment we show that this leads to significantly more accurate reconstructions, since map deformations due to systematic errors such as small camera calibration errors or outliers are well compensated. This again results in a better alignment of the augmentations during run-time of the application, even in large-scale environments.

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Keil, Jens; Zöllner, Michael; Becker, Mario; Wientapper, Folker; Engelke, Timo; Wuest, Harald

The House of Olbrich - An Augmented Reality Tour through Architectural History

2011

10th IEEE International Symposium on Mixed and Augmented Reality - Arts, Media, and Humanities

IEEE International Symposium on Mixed and Augmented Reality (ISMAR) <10, 2011, Basel, Switzerland>

With "House of Olbrich" we present an iPhone Augmented Reality (AR) app that visualizes the compelling history of Darmstadt's unique Jugendstil (Art Nouveau) quarter with video-see through Augmented Reality. We propose methods for enabling high performance computer vision algorithms to deploy sophisticated AR visuals on current generation Smartphones by outsourcing resource intensive tasks to the cloud. This allows us to apply methods on 3D feature recognition for even complex tracking situations outdoors, where lightning conditions change and tracked objects are often occluded. By taking a snapshot of the building, the user learns about the architect, design and history of the building. Historical media, like old photographs and blueprints are superimposed on the building's front, depicting the moved history of the famous House of Olbrich, which was destroyed during World War II and has been only rudimentary restored. Augmented Reality technology allows tourists to jump back in time visually by using their Smartphones: Mixing Realities emphasizes the user's experience and leads his attention to the impressive historical architecture of the Art Nouveau. In addition, we ease interaction means by superimposing snapshots. Tourists may view and read information also in a relaxed position without the need to front-up their mobiles all the time.

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Becker, Mario; Wuest, Harald; Wientapper, Folker; Engelke, Timo

A Prototyping Architecture for Augmented Reality

2009

2nd Workshop on Software Engineering and Architectures for Realtime Interactive Systems (SEARIS@VR2009)

Software Engineering and Architectures for Realtime Interactive Systems (SEARIS) <2, 2009, Lafayette, LA, USA>

In this paper we introduce an architecture for rapid development and assessment of advanced 3D visual track ing algorithms. We claim, that no universal tracking approach exists, that fulfills the requirements of all possible application seenarios at the same time. On the contrary, very specific and working solutions can be developed for given situations and uses. Therefore, software for visual tracking must be designed as a highly flexible system that can be quickly re-configured in order to enable the development of optimized solutions in terms of robustness, accuracy, frame rate and delay. To this purpose we designed an architecture that offers many functionalities, which can be combined together to build a new processing chain. The overall system offers numerous advantages, such as interactive programming, run-time access to data and parameters and easy interfacing with other libraries or applications.

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Wientapper, Folker; Ahrens, Katrin; Wuest, Harald; Bockholt, Ulrich

Linear-Projection-Based Classification of Human Postures in Time-of-Flight Data

2009

IEEE International Conference on Systems, Man and Cybernetics

IEEE International Conference on Systems, Man and Cybernetics (SMC) <2009, San Antonio, TX, USA>

This paper presents a simple yet effective approach for classification of human postures by using a time-of-flight camera. We investigate and adopt linear projection techniques such as Locality Preserving Projections (LPP), Linear Discriminant Analysis (LDA) and Principal Component Analysis (PCA), which are more widespread in face recognition and other pattern recognition tasks.We analyze the relations between LPP and LDA and show experimentally that using LPP in a supervised manner effectively yields very similar results as LDA, implying that LPP may be regarded as a generalization of LDA. Features for offline training and online classification are created by adopting common image processing techniques such as background-subtraction and blob detection to the time-of-flight data.

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Amoretti, Michele; Wientapper, Folker; Furfari, Francesco; Lenzi, Stefano; Chessa, Stefano

Sensor Data Fusion for Activity Monitoring in Ambient Assisted Living Environments

2009

The First International ICST Conference on Sensor Systems and Software. S-CUBE 2009 [CD-ROM]

International ICST Conference on Wireless Sensor Network (WSN) Systems and Software (S-CUBE) <1, 2009, Pisa, Italy>

We illustrate the PERSONA context-awareness framework applied to a major problem in Ambient Intelligence, namely user activity monitoring, that requires to infer new knowledge from collected and fused sensor data, dealing with highly dynamic environments where devices continuously change their availability and (or) physical location.We describe the Sensor Abstraction and Integration Layer (SAIL), we introduce the Human Posture Classification component, which is one particular context information provider, and finally we describe the Activity Monitor, which is a reasoner that delivers aggregated/derived context events in terms of the context ontology.

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Wuest, Harald; Wientapper, Folker; Stricker, Didier

Acquisition of High Quality Planar Patch Features

2008

Advances in Visual Computing. Proceedings Part I

International Symposium on Visual Computing (ISVC) <4, 2008, Las Vegas, NV, USA>

Camera-based tracking systems which reconstruct a feature map with structure from motion or SLAM techniques highly depend on the ability to track a single feature in different scales, different lighting conditions and a wide range of viewing angles. The acquisition of high quality features is therefore indispensable for a continuous tracking of a feature with a maximum possible range of valid appearances. We present a tracking system where not only the position of a feature but also its surface normal is reconstructed and used for precise prediction and tracking recovery of lost features. The appearance of a reference patch is also estimated sequentially and refined during the tracking, which leads to a more stable feature tracking step. Such reconstructed reference templates can be used for tracking a camera pose with a great variety of viewing positions. This feature reconstruction process is combined with a feature management system, where a statistical analysis of the ability to track a feature is performed, and only the most stable features for a given camera viewing position are used for the 2D feature tracking step. This approach results in a map of high quality features, where the real time capabilities can be preserved by only tracking the most necessary 2D feature points.

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Wuest, Harald; Wientapper, Folker; Stricker, Didier

Adaptable Model-Based Tracking Using Analysis-by-Synthesis Techniques

2007

Computer Analysis of Images and Patterns. Proceedings

International Conference on Computer Analysis of Images and Patterns (CAIP) <12, 2007, Vienna, Austria>

In this paper we present a novel analysis-by-synthesis approach for real-time camera tracking in industrial scenarios. The camera pose estimation is based on the tracking of line features which are generated dynamically in every frame by rendering a polygonal model and extracting contours out of the rendered scene. Different methods of the line model generation are investigated. Depending on the scenario and the given 3D model either the image gradient of the frame buffer or discontinuities of the z-buffer and the normal map are used for the generation of a 2D edge map. The 3D control points on a contour are calculated by using the depth value stored in the z-buffer. By aligning the generated features with edges in the current image, the extrinsic parameters of the camera are estimated. The camera pose used for rendering is predicted by a line-based frame-to-frame tracking which takes advantage of the generated edge features. The method is validated and evaluated with the help of ground-truth data as well as real image sequences.