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Department Talks

Appearance Modeling for 4D Multi-view Representations

Talk
  • 15 December 2017 • 12:00 12:45
  • Vagia Tsiminaki
  • PS Seminar Room (N3.022)

The emergence of multi-view capture systems has yield a tremendous amount of video sequences. The task of capturing spatio-temporal models from real world imagery (4D modeling) should arguably benefit from this enormous visual information. In order to achieve highly realistic representations both geometry and appearance need to be modeled in high precision. Yet, even with the great progress of the geometric modeling, the appearance aspect has not been fully explored and visual quality can still be improved. I will explain how we can optimally exploit the redundant visual information of the captured video sequences and provide a temporally coherent, super-resolved, view-independent appearance representation. I will further discuss how to exploit the interdependency of both geometry and appearance as separate modalities to enhance visual perception and finally how to decompose appearance representations into intrinsic components (shading & albedo) and super-resolve them jointly to allow for more realistic renderings.

Organizers: Despoina Paschalidou

  • Andrea Vedaldi
  • MPH Hall

Learnable representations, and deep convolutional neural networks (CNNs) in particular, have become the preferred way of extracting visual features for image understanding tasks, from object recognition to semantic segmentation. In this talk I will discuss several recent advances in deep representations for computer vision. After reviewing modern CNN architectures, I will give an example of a state-of-the-art network in text spotting; in particular, I will show that, by using only synthetic data and a sufficiently large deep model, it is possible directly map image regions to English words, a classification problem with 90K classes, obtaining in this manner state-of-the-art performance in text spotting. I will also briefly touch on other applications of deep learning to object recognition and discuss feature universality and transfer learning. In the last part of the talk I will move to the problem of understanding deep networks, which remain largely black boxes, presenting two possible approaches to their analysis. The first one are visualisation techniques that can investigate the information retained and learned by a visual representation. The second one is a method that allows exploring how representation capture geometric notions such as image transformations, and to find whether different representations are related and how.


  • Cristian Sminchisescu
  • MRZ Seminar room

Recent progress in computer-based visual recognition heavily relies on machine learning methods trained using large scale annotated datasets. While such data has made advances in model design and evaluation possible, it does not necessarily provide insights or constraints into those intermediate levels of computation, or deep structure, perceived as ultimately necessary in order to design reliable computer vision systems. This is noticeable in the accuracy of state of the art systems trained with such annotations, which still lag behind human performance in similar tasks. Nor does the existing data makes it immediately possible to exploit insights from a working system - the human eye - to derive potentially better features, models or algorithms. In this talk I will present a mix of perceptual and computational insights resulted from the analysis of large-scale human eye movement and 3d body motion capture datasets, collected in the context of visual recognition tasks (Human3.6M available at http://vision.imar.ro/human3.6m/, and Actions in the Eye available at http://vision.imar.ro/eyetracking/). I will show that attention models (fixation detectors, scan-paths estimators, weakly supervised object detector response functions and search strategies) can be learned from human eye movement data, and can produce state of the art results when used in end-to-end automatic visual recognition systems. I will also describe recent work in large-scale human pose estimation, showing the feasibility of pixel-level body part labeling from RGB, and towards promising 2D and 3D human pose estimation results in monocular images.In this context, I will discuss perceptual, perhaps surprising recent quantitative experiments, revealing that humans may not be significantly better than computers at perceiving 3D articulated poses from monocular images. Such findings may challenge established definitions of computer vision `tasks' and their expected levels of performance.


  • Benedetta Gennaro
  • MRC seminar room (0.A.03)

The breast is not just a protruding gland situated on the front of the thorax in female bodies: behind biology lies an intricate symbolism that has taken various and often contradictory meanings.  We begin our journey looking at pre-historic artifacts that revered the breast as the ultimate symbol of life; we then transition to the rich iconographical tradition centering on the so-called Virgo Lactans when the breast became a metaphor of nourishment for the entire Christian community. Next, we look at how artists have eroticized the breast in portraits of fifteenth-century French courtesans and how enlightenment philosophers and revolutionary events have transformed it into a symbol of the national community. Lastly, we analyze how contemporary society has medicalized the breast through cosmetic surgery and discourses around breast cancer, and has objectified it by making the breast a constant presence in advertisement and magazine covers. Through twenty-five centuries of representations, I will talk about how the breast has been coded as both "good" and "bad," sacred and erotic, life-giving and life-destroying.


  • Michael Tarr
  • MPH Lecture Hall

How is it that biological systems can be so imprecise, so ad hoc, and so inefficient, yet accomplish (seemingly) simple tasks that still elude state-of-the-art artificial systems? In this context, I will introduce some of the themes central to CMU's new BrainHub Initiative by discussing: (1) The complexity and challenges of studying the mind and brain; (2) How the study of the mind and brain may benefit from considering contemporary artificial systems; (3) Why studying the mind and brain might be interesting (and possibly useful) to computer scientists.


  • Paul G. Kry
  • MRC seminar room (0.A.03)

In this talk I will give an overview of work I have done over the years exploring physically based simulation of contact, deformation, and articulated structures where there are trade-offs between computational speed and physical fidelity that can be made.  I will also discuss examples that mix data-driven and physically based approaches in animation and control.

Paul Kry is an associate professor in the School of Computer Science at McGill University.  He has a BMath from University of Waterloo, and MSc and PhD from University of British Columbia.  His research focuses on physically based simulation, motion capture, and control of character animation.


What is biological motion?

Talk
  • 18 February 2015 • 15:00:00
  • Nikolaus F. Troje
  • MRC seminar room (0.A.03)

Everyone in visual psychology seems to know what Biological Motion is. Yet, it is not easy to come up with a definition that is specific enough to justify a distinct label, but is also general enough to include the many different experiments to which the term has been applied in the past. I will present a number of tasks, stimuli, and experiments, including some of my own work, to demonstrate the diversity and the appeal of the field of biological motion perception. In trying to come up with a definition of the term, I will particularly focus on a type of motion that has been considered “non-biological” in some contexts, even though it might contain -- as more recent work shows -- one of the most important visual invariants used by the visual system to distinguish animate from inanimate motion.


Reconstructing Complete 3D Models from Single Images

Talk
  • 17 February 2015 • 09:00:00
  • Vladlen Koltun
  • MRC seminar room (0.A.03)

We present an approach to creating 3D models of objects depicted in Web images, even when each object may only be shown in a single image. Our approach uses a comparatively small collection of existing 3D models to guide the reconstruction process. These existing shapes are used to derive information about shape structure. Our guiding idea is to jointly analyze the images and the available 3D models. Joint analysis of all images along with the available shapes regularizes the formulated optimization problems, stabilizes estimation of camera parameters and construction of dense pixel-level correspondences, and leads to reasonable reproduction of object appearance in the absence of traditional multi-view cues. Joint work with Qixing Huang and Hai Wang.


Reflecting in and on the Gradient Domain

IS Colloquium
  • 16 February 2015 • 10:15:00
  • Michael Goesele
  • MPH Hall

Image-based rendering has been introduced in the 1990s as an alternative approach to photorealistic rendering. Its key idea is to novel renderings by re-projecting pixels from nearby views. The basic approach works well for many scenes but breaks down if the scene contains “non-standard” elements such as reflective surfaces. In this talk, I will first show how we can extend image-based rendering to handle scenes with reflections. I will then discuss a novel gradient-based technique for image-based rendering that can intrinsically handle scenes with reflections.


  • Wenzel Jakob
  • MRZ seminar room

Driven by the increasing demand for photorealistic computer-generated images, graphics is currently undergoing a substantial transformation to physics-based approaches which accurately reproduce the interaction of light and matter. Progress on both sides of this transformation -- physical models and simulation techniques -- has been steady but mostly independent from another. When combined, the resulting methods are in many cases impracticably slow and require unrealistic workarounds to process even simple everyday scenes. My research lies at the interface of these two research fields; my goal is to break down the barriers between simulation techniques and the underlying physical models, and to use the resulting insights to develop realistic methods that remain efficient over a wide range of inputs.

I will cover three areas of recent work: the first involves volumetric modeling approaches to create realistic images of woven and knitted cloth. Next, I will discuss reflectance models for glitter/sparkle effects and arbitrarily layered materials that are specially designed to allow for efficient simulations. In the last part of the talk, I will give an overview of Manifold Exploration, a Markov Chain Monte Carlo technique that is able to reason about the geometric structure of light paths in high dimensional configuration spaces defined by the underlying physical models, and which uses this information to compute images more efficiently.


  • Konrad Schindler
  • Max Planck House Lecture Hall

I will present selected research projects of the Photogrammetry and Remote Sensing Group at ETH, including (i) 3D scene flow estimation for stereo video captured from a car; (ii) extraction of road networks from aerial images; and (iii) 3D reconstruction from large, unstructured (e.g. crowd-sourced) image collections.