Events & Talks

Perceiving Systems Talk 09-07-2012 Complex Data Spaces: 3D Pose Reconstruction using Manifold Embedding and Recognition of Facial Expressions using Conditional Random Fields

Perceiving Systems Talk 26-06-2012 Biologically-inspired learning-based models for the recognition and synthesis of interactive body movements Human body movements are highly complex spatio-temporal patterns and their control and recognition represent challenging problems for technical as well as neural systems. The talk will present an overview of recent work of our group, exploiting biologically-inspired learning-based reprensentations for the recognition and synthesis of body motion. The first part of the talk will present a neural theory for the visual processing of goal-directed actions, which reproduces and partially correctly predicts electrophysiological results from action-selective cortical neurons in m...

Perceiving Systems Talk 09-05-2012 Object Recognition and Shape Reconstruction under Complex Lighting Variations in lighting can have a significant effect on the appearance of an object. Modeling these variations is important for object recognition and shape reconstruction, particularly of smooth, textureless objects. The recent decade has seen significant progress in handling lambertian objects. In that context I will present our work on using harmonic representations to represent the reflectance of lambertian objects under complex lighting configurations and their application to photometric stereo and prior-assisted shape from shading. In addition, I will present preliminary results...

Perceiving Systems Talk 02-05-2012 Exploring the role of ventral premotor cortex in reach-to-grasp movements: neural trajectories through spike train similarity space Dimensionality reduction applied to neural ensemble data has led to the concept of a 'neural trajectory', a low-dimensional representation of how the state of the network evolves over time. Here we present a novel neural trajectory extraction algorithm which combines spike train distance metrics (Victor and Purpura, 1996) with dimensionality reduction based on local neighborhood statistics (van der Maaten and Hinton, 2008.) . We apply this technique to describe and quantify the activity of primate ventral premotor cortex neuronal ensembles in the context of a cued reaching and...

Perceiving Systems Talk 18-04-2012 A Modular, Multimodal Arm Model: Multisensory Integration and Flexible Motion Control Humans interact with their environment in a highly flexible manner. One important component for the successful control of such flexible interactions is an internal body model. To maintain a consistent internal body model, the brain appears to continuously and probabilistically integrate multiple sources of information, including various sensory modalities but also anticipatory, re-afferent information about current body motion. A modular, multimodal arm model (MMM) is presented. The model represents a seven degree of freedom arm in various interactive modality frames. The ...

Perceiving Systems Talk 16-04-2012 Actions Recognition from Videos: Some Recent Results Cordelia Schmid INRIA The amount of digital video content available is growing daily, on sites such as YouTube. Recent statistics on the YouTube website show that around 48 hours of video are uploaded every minute. This massive data production calls for automatic analysis. In this talk we present some recent results for action recognition in videos. Bag-of-features have shown very good performance for action recognition in videos. We briefly review the underlying principles and introduce trajectory-based video features, which have shown to outperform the state of the art. These trajectory feature...

Perceiving Systems Talk 15-03-2012 Information-driven Surveillance The supervision of public spaces aims at multiple objectives, such as early acquisition of targets, their identification and pursuit throughout the supervised area. To achieve these, typical sensors such as pan-tilt-zoom cameras need to either focus on individuals, or provide a broad field of view, which are conflicting control settings. We address this problem in an information-theoretic manner: by phrasing each of the objectives in terms of mutual information, they become comparable. The problem turns into maximisation of information, which is predicted for the next time step and ph...

Perceiving Systems Talk 13-02-2012 Algorithms for low-cost depth imaging Recovering the depth of a scene is important for bridging the gap between the real and the virtual world, but also for tasks such as segmenting objects in cluttered scenes. Very cheap single view depth imaging cameras, i.e. Time of Fight cameras (ToF) or Microsoft's Kinect system, are entering the mass consumer market. In general, the acquired images have a low spatial resolution and suffer from noise as well as technology specific artifacts. In this talk I will present algorithmic solutions to the entire depth imaging pipeline, ranging from preprocessing to depth image analysis. ...

Perceiving Systems Talk 09-02-2012 One-shot Dense 3D Reconstruction for Objects in Fast Motion 3D scanning of moving objects has many applications, for example, marker-less motion capture, analysis on fluid dynamics, object explosion and so on. One of the approach to acquire accurate shape is a projector-camera system, especially the methods that reconstructs a shape by using a single image with static pattern is suitable for capturing fast moving object. In this research, we propose a method that uses a grid pattern consisting of sets of parallel lines. The pattern is spatially encoded by a periodic color pattern. While informations are sparse in the camera image, the proposed ...

Perceiving Systems Talk 24-01-2012 Optimal Landmark Detection using Shape Models and Branch and Bound Fitting statistical 2D and 3D shape models to images is necessary for a variety of tasks, such as video editing and face recognition. Much progress has been made on local fitting from an initial guess, but determining a close enough initial guess is still an open problem. One approach is to detect distinct landmarks in the image and initialize the model fit from these correspondences. This is difficult, because detection of landmarks based only on their local appearance is inherently ambiguous, making it necessary to use global shape information for the detections. We propose a method ...

Perceiving Systems Talk 23-01-2012 Physics-Based Models for Human Motion Analysis This talk concerns the use of physics-based models for human pose tracking and scene inference. We outline our motivation for physics-based models, some results with monocular pose tracking in terms of biomechanically inspired controllers, and recent results on the inference of scene interactions. We show that physics-based models facilitate the estimation of physically plausible human motion with little or no mocap data required. Scene interactions play an integral role in modeling sources of external forces acting on the body.

Perceiving Systems Talk 02-12-2011 Context in image (and video) understanding In spite of the significant effort that has been devoted to the core problems of object and action recognition in images and videos, the recognition performance of state of the art algorithms is well below what would be required for any successful deployment in many applications. Additionally, there are challenging combinatorial problems associated with constructing globally “optimal” descriptions of images and videos in terms of potentially very large collections of object and action models. The constraints that are utilized in these optimization procedures are loosely r... Michel Besserve

Perceiving Systems Talk 16-11-2011 Efficient Human Pose Estimation with Higher-order Image Information Human pose estimation from monocular images is one of the most challenging and computationally demanding problems in computer vision. Standard models such as Pictorial Structures consider interactions between kinematically-connected joints or limbs, leading to inference quadratic in the number of pixels. As a result, researchers and practitioners have restricted themselves to simple models which only measure the quality of limb-pair possibilities by their 2D geometric plausibility. In this talk, we propose novel methods which allow for efficient inference in richer models... Michel Besserve

Perceiving Systems Talk 03-11-2011 3D Human Motion Estimation Inside and Out Pose estimation and tracking has been a focus of computer vision research for many years. Despite many successes, however, most approaches to date are still not able to recover physically realistic (natural looking) 3d motions and are restricted to captures indoors or with simplified backgrounds. In the first part of this talk, I will briefly introduce a class of models that use physics to constrain the motion of the subject to more realistic interpretations. In particular, we formulate the pose tracking problem as one of inference of control mechanisms which implicitly (t... Michel Besserve

Max Planck Lecture 14-10-2011 Evolution of cooperation Cooperation implies that one individual pays a cost for another to receive a benefit. Cost and benefit are measured in terms of reproductive success. Cooperation is useful for construction in evolution: genomes, cells, multi-cellular organisms, animal and human societies are consequences of cooperation. Cooperation can be at variance with natural selection. Why should you help competitors?

Perceiving Systems Talk 26-09-2011 Isometry-Invariant Shape Analysis Shape analysis aims to describe either a single shape or a population of shapes in an efficient and informative way. This is a key problem in various applications such as mesh deformation and animation, object recognition, and mesh parameterization. I will present a number of approaches to process shapes that are nearly isometric. The first approach computes the correspondence information between a population of shapes in this setting. Second and third are approaches to morph between two shapes and to segment a population of shapes into near-rigid components. Next, I will ...

Perceiving Systems Talk 21-09-2011 A Geometric Approach to Human Motion Modelling We propose a geometric approach to articulated tracking, where the human pose representation is expressed on the Riemannian manifold of joint positions. This is in contrast to conventional methods where the problem is phrased in terms of intrinsic parameters of the human pose. Our model is based on a physically natural metric that also has strong links to neurological models of human motion planning. Some benefits of the model is that it allows for easy modeling of interaction with the environment, for data-driven optimization schemes and for well-posed low-pass filtering properties.... Michel Besserve

Perceiving Systems Talk 19-09-2011 Non-Rigid Registration in Entertainment and Science A pure refinement procedure for non-rigid registration can be highly effective for establishing dense correspondences between pairs of scanned data, even for significant deformations. I will explain how to design robust non-rigid algorithms and why it is important to couple the optimization of correspondence positions, warping field, and overlapping regions. I will show several applications where it has been successfully applied ranging from film/game production to radiation oncology. One particular interest of mine is facial animation. I will present a fully integrated system for re... Gerard Pons-Moll

Perceiving Systems Talk 08-09-2011 There and Back Again or Academia vs. the Visual Effects Industry Many machine vision/image processing algorithms are designed to be real-time and fully automatic. These attributes are essential, e.g., for stereo robotics vision applications. Visual Effects Studios, however, posses giant server farms and command armies of artists to perform intelligent initialization or provide guidance to algorithms. On the other hand, motion pictures have very high accuracy requirements and the ability to influence an algorithm manually is often more important than other factors, generally considered crucial in Academia. In this talk I will highlight some scenari... Michel Besserve Gerard Pons-Moll

Perceiving Systems Talk 06-09-2011 3D Shape Segmentation and Matching using Graph Spectral Methods In the era of perpetually increasing computational capabilities, multi-camera acquisition systems are being increasingly used to capture parameterization-free articulated 3D shapes. These systems allow marker-less shape acquisition and are useful for a wide range of applications in the entertainment, sports, surveillance industries and also in interactive, and augmented reality systems. The availability of vast amount of 3D shape data has increased interest in 3D shape analysis methods. Segmentation and Matching are two important shape analysis tasks. 3D shape segmentation is a subjec... Sebastian Trimpe

Perceiving Systems Talk 18-08-2011 Capturing and Modeling Human Interactions Capturing human motion or objects by vision technology has been intensively studied. Although humans interact very often with other persons or objects, most of the previous work has focused on capturing a single object or the motion of a single person. In this talk, I will highlight four projects that deal with human-human or human-object interactions. The first project addresses the problem of capturing skeleton and non-articulated cloth motion of two interacting characters. The second project aims to model spatial hand-object relations during object manipulation. In the third projec... Philipp Hennig Michel Besserve

Perceiving Systems Talk 01-08-2011 Recovering Intrinsic Images / Efficient Object Detection n this talk I will present recent work on two different topics from low- and high-level computer vision: Intrinsic Image Recovery and Efficient object detection. By intrinsic image decomposition we refer to the challenging task of decoupling material properties from lighting properties given a single image. We propose a probabilistic model that incorporates previous attempts exploiting edge information and combine it with a novel prior on material reflectances in the image. This results in a random field model with global, latent variables and pixel-accurate output reflectance values...

Perceiving Systems Talk 18-07-2011 3D Isometric Shape Correspondence 3D shape correspondence methods seek on two given shapes for pairs of surface points that are semantically equivalent. We present three automatic algorithms that address three different aspects of this problem: 1) coarse, 2) dense, and 3) partial correspondence. In 1), after sampling evenly-spaced base vertices on shapes, we formulate the problem of shape correspondence as combinatorial optimization over the domain of all possible mappings of bases, which then reduces within a probabilistic framework to a log-likelihood maximization problem that we solve via EM (Expectation Maximizati...

Perceiving Systems Talk 04-07-2011 Visual Recognition with Humans in the Loop We present an interactive, hybrid human-computer method for object classification. The method applies to classes of problems that are difficult for most people, but are recognizable by people with the appropriate expertise (e.g., animal species or airplane model recognition). The classification method can be seen as a visual version of the 20 questions game, where questions based on simple visual attributes are posed interactively. The goal is to identify the true class while minimizing the number of questions asked, using the visual content of the image. Incorporating us...

Perceiving Systems Talk 14-06-2011 Learning Components for Human Sensing Enabling computers to understand human behavior has the potential to revolutionize many areas that benefit society such as clinical diagnosis, human computer interaction, and social robotics. A critical element in the design of any behavioral sensing system is to find a good representation of the data for encoding, segmenting, classifying and predicting subtle human behavior. In this talk I will propose several extensions of Component Analysis (CA) techniques (e.g., kernel principal component analysis, support vector machines, spectral clustering) that are able to learn spatio...

Perceiving Systems Talk 14-06-2011 Sensing, modeling and executing object manipulation Object grasping and manipulation is a crucial part of daily human activities. The study of these actions represents a central component in the development of systems that attempt to understand human activities and robots that are able to act in human environments. Three essential parts of this problem are tackled in this talk: the perception of the human hand in interaction with objects, the modeling of human grasping actions and the refinement of the execution of a robotic grasp. The estimation of the human hand pose is carrried out with a markerless visual system that pe...

Perceiving Systems Talk 24-05-2011 Colloidal Semiconductor Nanocrystals as Light Emitters in the Red, Green, and Blue: Device Prospects from Single Photon Emitters to Laser Devices Semiconductor light emitters, based on single crystal epitaxial inorganic semiconductor heterostructures are ubiquitous. In spite of their extraordinary versatility and technological maturity, penetrating the full visible spectrum using a single material system for red, green, and blue (RGB) in a seamless way remains, nonetheless, an elusive challenge. Semiconductor nanocrystals, or quantum dots (QDs), synthesized by solution-based methods of colloidal chemistry represent a strongly contrasting basis for active optical materials. While possessing an ability to absorb and ef...

Perceiving Systems Talk 23-05-2011 Emerging Neurotechnologies for Interfacing the Brain Invasive access by microprobe arrays inserted safely into the brain is now enabling us to “listen” to local neural circuits at levels of spatial and temporal detail which, in addition to enriching fundamental brain science, has led to the possibility of a new generation of neurotechnologies to overcome disabilities due to a range of neurological injuries where pathways from the brain to the rest of the central and peripheral nervous systems have been injured or severed. In this presentation we discuss the biomedical engineering challenges and opportunities with these inci...

Perceiving Systems Talk 13-05-2011 Capturing and Synthesizing Hand-Object Interaction The scope of this work is hand-object interaction. As a starting point, we observe hands manipulating objects and derive information based on computer vision methods. After considering hands and objects in isolation, we focus on the inherent interdependencies. One application of the gained knowledge is the synthesis of interactive hand motion for animated sequences.

Perceiving Systems Talk 22-04-2011 Toward Autonomous Visual Learning Vision is a crucial sense for computational systems to interact with their environments as biological systems do. A major task is interpreting images of complex scenes, by recognizing and localizing objects, persons and actions. This involves learning a large number of visual models, ideally autonomously. In this talk I will present two ways of reducing the amount of human supervision required by this learning process. The first way is labeling images only by the object class they contain. Learning from cluttered images is very challenging in this weakly supervised setting....

Perceiving Systems Talk 19-04-2011 Tracking and Measurement in Sports Video I will survey our work on tracking and measurement, waypoints on the path to activity recognition and understanding, in sports video, highlighting some of our recent work on rectification and player tracking, not just in hockey but more recently in basketball, where we have addressed player identification both in a fully supervised and semi-supervised manner.

Perceiving Systems Talk 18-04-2011 Learning Representations for Real-world Recognition Methods for visual recognition have made dramatic strides in recent years on various online benchmarks, but performance in the real world still often falters. Classic gradient-histogram models make overly simplistic assumptions regarding image appearance statistics, both locally and globally. Recent progress suggests that new learning-based representations can improve recognition by devices that are embedded in a physical world. I'll review new methods for domain adaptation which capture the visual domain shift between environments, and improve recognition of objects in s...

Perceiving Systems Talk 15-04-2011 Algorithms for Detection, Tracking, Analysis, and Classification of Objects and Human Actions In the first part of the talk, I will describe methods that learn a single family of detectors for object classes that exhibit large within-class variation. One common solution is to use a divide-and-conquer strategy, where the space of possible within-class variations is partitioned, and different detectors are trained for different partitions. However, these discrete partitions tend to be arbitrary in continuous spaces, and the classifiers have limited power when there are too few training samples in each subclass. To address this shortcoming, explicit feature sharing h...

Max Planck Lecture 03-03-2011 The advent of mesoscopic solar cells The field of photovoltaic cells has been dominated so far by solid state p-n junction devices made e.g. of crystalline or amorphous silicon, profiting from the experience and material availability of the semiconductor industry. However, there is an increasing awareness of the possible advantages of devices referred to as "bulk" junctions due to their interconnected three-dimensional structure. Their embodiment departs completely from the conventional flat p-n junction solid-state cells, replacing them by interpenetrating networks.

Max Planck Lecture 27-05-2010 Materials Science Aproaches for Life Sciences and Human Health This lecture will provide recent research results at the intersections of engineering, materials science, nanotechnology, genetics, life sciences, medicine and public health.

Max Planck Lecture 23-11-2009 Atomic Engineering Oxide Heterointerfaces Complex oxides are fascinating systems which host a vast array of unique phenomena, such as high-temperature (and unconventional) superconductivity, "colossal" magnetoresistance, all forms of magnetism and ferroelectricity, as well as (quantum) phase transitions and couplings between these states.

Max Planck Lecture 08-06-2009 Architectured Materials and Multifunctional Designs: Foams, Wools and Interlocked Materials Developing new materials via a better understanding of the mechanisms underlying macroscopic properties has been the Graal of materials science. The most prominent effort in Materials Science has been toward a better control of the microstructure, toward smaller and smaller scales, and in recent years, toward nanomaterials.

Max Planck Lecture 15-10-2008 Electron Interference in two Dimensions: Phase Measurements, Controlled Dephasing and Phase Recovery Electron interference in the solid enables to determine the electron coherence time, the phase electron gains during transport, the statistics of quasi-particles in strongly interacting systems, and the processes of dephasing.

Max Planck Lecture 22-07-2008 Nanocrystals as Model Systems for Understanding Structural and Chemical Transformations in the Solid State The advent of means to prepare well-controlled nanoscale building blocks has opened up many new opportunities to understand difficult problems which lie at the core of materials science. As an example, nanometer-size inorganic nanocrystals can be transformed from one state to another with remarkably simplified kinetics compared to extended or bulk solids.

Max Planck Lecture 11-07-2007 Nanowire Building Blocks for Photonics & Energy Conversion Nanowires are of both fundamental and technological interest. They represent the critical components in the potential nanoscale electronic and photonic device applications.

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