430 research outputs found
Transformation Optics and the Geometry of Light
Metamaterials are beginning to transform optics and microwave technology
thanks to their versatile properties that, in many cases, can be tailored
according to practical needs and desires. Although metamaterials are surely not
the answer to all engineering problems, they have inspired a series of
significant technological developments and also some imaginative research,
because they invite researchers and inventors to dream. Imagine there were no
practical limits on the electromagnetic properties of materials. What is
possible? And what is not? If there are no practical limits, what are the
fundamental limits? Such questions inspire taking a fresh look at the
foundations of optics and at connections between optics and other areas of
physics. In this article we discuss such a connection, the relationship between
optics and general relativity, or, expressed more precisely, between
geometrical ideas normally applied in general relativity and the propagation of
light, or electromagnetic waves in general, in materials. We also discuss how
this connection is applied: in invisibility devices, perfect lenses, the
optical Aharonov-Bohm effect of vortices and in analogues of the event horizon.Comment: 72 pages, 18 figures, preprint with low-resolution images.
Introduction to transformation optics, to appear in Progress in Optics
(edited by Emil Wolf
Fast soft-tissue deformations with FEM
Soft body simulation has been a very active research area in computer animation since Baraff and Witkin's 1998 work on cloth simulation, which led Pixar to start using such techniques in all of its animated movies that followed. Many challenges in these simulations come from different roots. From a numerical point of view, deformable systems are large sparse problems that can become numerically unstable at surprising rates and may need to be modified at each time-step. From a mathematical point of view, hyperelastic models defined by continuum mechanics need to be derived, established and configured. And from the geometric side, physical interaction with the environment and self-collisions may need to be detected and introduced into the solver. It is a fact that the Computer Graphics academia primarily focuses on offline methods, both for rendering and simulation. At the same time, the advances from the industry mainly apply to real-time rendering. However, we wondered how such high-quality simulation methods would map to a real-time use case. In this thesis, we delve into the simulation system used by Pixar's Fizt2 simulator, based on the Finite Element Method, and investigate how to apply the same techniques in real-time while preserving robustness and fidelity, altogether providing the user with some interaction mechanisms. A 3D engine for simulating deformable materials has been developed following the described models, with an interactive interface that allows the definition and configuration of scenes and later interaction with the simulation
Spatially Adaptive Computation Time for Residual Networks
This paper proposes a deep learning architecture based on Residual Network
that dynamically adjusts the number of executed layers for the regions of the
image. This architecture is end-to-end trainable, deterministic and
problem-agnostic. It is therefore applicable without any modifications to a
wide range of computer vision problems such as image classification, object
detection and image segmentation. We present experimental results showing that
this model improves the computational efficiency of Residual Networks on the
challenging ImageNet classification and COCO object detection datasets.
Additionally, we evaluate the computation time maps on the visual saliency
dataset cat2000 and find that they correlate surprisingly well with human eye
fixation positions.Comment: CVPR 201
DELTAS: Depth Estimation by Learning Triangulation And densification of Sparse points
Multi-view stereo (MVS) is the golden mean between the accuracy of active
depth sensing and the practicality of monocular depth estimation. Cost volume
based approaches employing 3D convolutional neural networks (CNNs) have
considerably improved the accuracy of MVS systems. However, this accuracy comes
at a high computational cost which impedes practical adoption. Distinct from
cost volume approaches, we propose an efficient depth estimation approach by
first (a) detecting and evaluating descriptors for interest points, then (b)
learning to match and triangulate a small set of interest points, and finally
(c) densifying this sparse set of 3D points using CNNs. An end-to-end network
efficiently performs all three steps within a deep learning framework and
trained with intermediate 2D image and 3D geometric supervision, along with
depth supervision. Crucially, our first step complements pose estimation using
interest point detection and descriptor learning. We demonstrate
state-of-the-art results on depth estimation with lower compute for different
scene lengths. Furthermore, our method generalizes to newer environments and
the descriptors output by our network compare favorably to strong baselines.
Code is available at https://github.com/magicleap/DELTASComment: ECCV 202
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