Animation en volume | EPFL Graph Search

L'animation en volume ou animation pas-à-pas (également désignée par le terme anglais stop motion) est une technique d'animation utilisée avec des objets réels, dotés de volume. Alors que les objets sont immobiles en eux-mêmes, cette technique permet de créer l'illusion qu'ils sont dotés d'un mouvement naturel. Différents types d'objets sont utilisés à cette fin : des figurines articulées, des maquettes articulées, du papier plié, de la pâte à modeler, etc. Des exemples célèbres de films ayant recouru à cette technique sont King Kong (1933), de nombreux films fantastiques de la seconde moitié du siècle dont ceux du célèbre Ray Harryhausen (1920-2013) ou, plus récemment, L'Île aux chiens (2018), de Wes Anderson, parmi bien d'autres exemples. Dans la plupart des œuvres visuelles où cette technique est utilisée, un décor constitué d’objets est filmé à l’aide d’une caméra dédiée à l’animation, c’est-à-dire pouvant enregistrer sur une pellicule cinématographique un seul photogramme chaq

How to Stop Under-Utilization and Love Multicores

Anastasia Ailamaki, Erietta Liarou, Danica Porobic, Iraklis Psaroudakis, Pinar Tözün

Designing scalable transaction processing systems on modern hardware has been a challenge for almost a decade. Hardware trends oblige software to overcome three major challenges against systems scalability: (1) Exploiting the abundant thread-level parallelism provided by multicores, (2) Achieving predictively efficient execution despite the variability in communication latencies among cores on multisocket multicores, and (3) Taking advantage of the aggressive micro-architectural features. In this tutorial, we shed light on the above three challenges and survey recent proposals to alleviate them. First, we present a systematic way of eliminating scalability bottlenecks based on minimizing unbounded communication and show several techniques that apply the presented methodology to minimize bottlenecks in major components of transaction processing systems. Then, we analyze the problems that arise from the non-uniform nature of communication latencies on modern multisockets and ways to address them for systems that already scale well on multicores. Finally, we examine the sources of under-utilization within a modern processor and present insights and techniques to better exploit the micro-architectural resources of a processor by improving cache locality at the right level.

2014

How to Stop Under-Utilization and Love Multicores

Anastasia Ailamaki, Erietta Liarou, Danica Porobic, Iraklis Psaroudakis, Pinar Tözün

Hardware trends oblige software to overcome three major challenges against systems scalability: (1) taking advantage of the implicit/vertical parallelism within a core that is enabled through the aggressive micro-architectural features, (2) exploiting the explicit/horizontal parallelism provided by multicores, and (3) achieving predictively efficient execution despite the variability in communication latencies among cores on multisocket multicores. In this three hour tutorial, we shed light on the above three challenges and survey recent proposals to alleviate them. The first part of the tutorial describes the instruction- and data-level parallelism opportunities in a core coming from the hardware and software side. In addition, it examines the sources of under-utilization in a modern processor and presents insights and hardware/software techniques to better exploit the microarchitectural resources of a processor by improving cache locality at the right level of the memory hierarchy. The second part focuses on the scalability bottlenecks of database applications at the level of multicore and multisocket multicore architectures. It first presents a systematic way of eliminating such bottlenecks in online transaction processing workloads, which is based on minimizing unbounded communication, and shows several techniques that minimize bottlenecks in major components of database management systems. Then, it demonstrates the data and work sharing opportunities for analytical workloads, and reviews advanced scheduling mechanisms that are aware of nonuniform memory accesses and alleviate bandwidth saturation.

2015

Using biomechanical constraints to improve video-based motion capture

Lorna Herda

In motion capture applications whose aim is to recover human body postures from various input, the high dimensionality of the problem makes it desirable to reduce the size of the search-space by eliminating a priori impossible configurations. This can be carried out by constraining the posture recovery process in various ways. Most recent work in this area has focused on applying camera viewpoint-related constraints to eliminate erroneous solutions. When camera calibration parameters are available, they provide an extremely efficient tool for disambiguating not only posture estimation, but also 3D reconstruction and data segmentation. Increased robustness is indeed to be gained from enforcing such constraints, which we prove in the context of an optical motion capture framework. Our contribution in this respect resides in having applied such constraints consistently to each main step involved in a motion capture process, namely marker reconstruction and segmentation, followed by posture recovery. These steps are made inter-dependent, where each one constrains the other. A more application-independent approach is to encode constraints directly within the human body model, such as limits on the rotational joints. This being an almost unexplored research subject, our efforts were mainly directed at determining a new method for measuring, representing and applying such joint limits. To the present day, the few existing range of motion boundary representations present severe drawbacks that call for an alternative formulation. The joint limits paradigm we propose not only overcomes these drawbacks, but also allows to capture intra- and inter-joint rotation dependencies, these being essential to realistic joint motion representation. The range of motion boundary is defined by an implicit surface, its analytical expression enabling us to readily establish whether a given joint rotation is valid or not. Furthermore, its continuous and differentiable nature provides us with a means of elegantly incorporating such a constraint within an optimisation process for posture recovery. Applying constrained optimisation to our body model and stereo data extracted from video sequence, we demonstrate the clearly resulting decrease in posture estimation errors. As a bonus, we have integrated our joint limits representation in character animation packages to show how motion can be naturally constrained in this manner.

EPFL2004

Using biomechanical constraints to improve video-based motion capture

Lorna Herda

EPFL2004