51 research outputs found
UCLID-Net: Single View Reconstruction in Object Space
Most state-of-the-art deep geometric learning single-view reconstruction
approaches rely on encoder-decoder architectures that output either shape
parametrizations or implicit representations. However, these representations
rarely preserve the Euclidean structure of the 3D space objects exist in. In
this paper, we show that building a geometry preserving 3-dimensional latent
space helps the network concurrently learn global shape regularities and local
reasoning in the object coordinate space and, as a result, boosts performance.
We demonstrate both on ShapeNet synthetic images, which are often used for
benchmarking purposes, and on real-world images that our approach outperforms
state-of-the-art ones. Furthermore, the single-view pipeline naturally extends
to multi-view reconstruction, which we also show.Comment: Added supplementary materia
Gestion de maillages triangulaires déformables
On présente un algorithme permettant à la fois de contrôler et d'améliorer le maillage d'une géométrie déformable au cours du temps. Un critère géométrique portant sur la déformation des éléments triangulaires permet de mesurer, de façons locale et globale, la qualité du maillage. La première étape consiste en une régularisation par retournement d'arêtes tant que cela est possible. Il convient ensuite de regrouper les éventuels triangles restant afin de constituer des zones que l'on remaillera grâce à un algorithme de voronoï 2D après avoir créé un (des) trou(s) dans le maillage. Cette présentation est illustrée par des exemples appliqués au moteur automobile
Learning to Simulate Realistic LiDARs
Simulating realistic sensors is a challenging part in data generation for
autonomous systems, often involving carefully handcrafted sensor design, scene
properties, and physics modeling. To alleviate this, we introduce a pipeline
for data-driven simulation of a realistic LiDAR sensor. We propose a model that
learns a mapping between RGB images and corresponding LiDAR features such as
raydrop or per-point intensities directly from real datasets. We show that our
model can learn to encode realistic effects such as dropped points on
transparent surfaces or high intensity returns on reflective materials. When
applied to naively raycasted point clouds provided by off-the-shelf simulator
software, our model enhances the data by predicting intensities and removing
points based on the scene's appearance to match a real LiDAR sensor. We use our
technique to learn models of two distinct LiDAR sensors and use them to improve
simulated LiDAR data accordingly. Through a sample task of vehicle
segmentation, we show that enhancing simulated point clouds with our technique
improves downstream task performance.Comment: IROS2022 pape
PDRs4All III: JWST's NIR spectroscopic view of the Orion Bar
(Abridged) We investigate the impact of radiative feedback from massive stars
on their natal cloud and focus on the transition from the HII region to the
atomic PDR (crossing the ionisation front (IF)), and the subsequent transition
to the molecular PDR (crossing the dissociation front (DF)). We use
high-resolution near-IR integral field spectroscopic data from NIRSpec on JWST
to observe the Orion Bar PDR as part of the PDRs4All JWST Early Release Science
Program. The NIRSpec data reveal a forest of lines including, but not limited
to, HeI, HI, and CI recombination lines, ionic lines, OI and NI fluorescence
lines, Aromatic Infrared Bands (AIBs including aromatic CH, aliphatic CH, and
their CD counterparts), CO2 ice, pure rotational and ro-vibrational lines from
H2, and ro-vibrational lines HD, CO, and CH+, most of them detected for the
first time towards a PDR. Their spatial distribution resolves the H and He
ionisation structure in the Huygens region, gives insight into the geometry of
the Bar, and confirms the large-scale stratification of PDRs. We observe
numerous smaller scale structures whose typical size decreases with distance
from Ori C and IR lines from CI, if solely arising from radiative recombination
and cascade, reveal very high gas temperatures consistent with the hot
irradiated surface of small-scale dense clumps deep inside the PDR. The H2
lines reveal multiple, prominent filaments which exhibit different
characteristics. This leaves the impression of a "terraced" transition from the
predominantly atomic surface region to the CO-rich molecular zone deeper in.
This study showcases the discovery space created by JWST to further our
understanding of the impact radiation from young stars has on their natal
molecular cloud and proto-planetary disk, which touches on star- and planet
formation as well as galaxy evolution.Comment: 52 pages, 30 figures, submitted to A&
PDRs4All II: JWST's NIR and MIR imaging view of the Orion Nebula
The JWST has captured the most detailed and sharpest infrared images ever
taken of the inner region of the Orion Nebula, the nearest massive star
formation region, and a prototypical highly irradiated dense photo-dissociation
region (PDR). We investigate the fundamental interaction of far-ultraviolet
photons with molecular clouds. The transitions across the ionization front
(IF), dissociation front (DF), and the molecular cloud are studied at
high-angular resolution. These transitions are relevant to understanding the
effects of radiative feedback from massive stars and the dominant physical and
chemical processes that lead to the IR emission that JWST will detect in many
Galactic and extragalactic environments. Due to the proximity of the Orion
Nebula and the unprecedented angular resolution of JWST, these data reveal that
the molecular cloud borders are hyper structured at small angular scales of
0.1-1" (0.0002-0.002 pc or 40-400 au at 414 pc). A diverse set of features are
observed such as ridges, waves, globules and photoevaporated protoplanetary
disks. At the PDR atomic to molecular transition, several bright features are
detected that are associated with the highly irradiated surroundings of the
dense molecular condensations and embedded young star. Toward the Orion Bar
PDR, a highly sculpted interface is detected with sharp edges and density
increases near the IF and DF. This was predicted by previous modeling studies,
but the fronts were unresolved in most tracers. A complex, structured, and
folded DF surface was traced by the H2 lines. This dataset was used to revisit
the commonly adopted 2D PDR structure of the Orion Bar. JWST provides us with a
complete view of the PDR, all the way from the PDR edge to the substructured
dense region, and this allowed us to determine, in detail, where the emission
of the atomic and molecular lines, aromatic bands, and dust originate
A far-ultraviolet-driven photoevaporation flow observed in a protoplanetary disk
Most low-mass stars form in stellar clusters that also contain massive stars,
which are sources of far-ultraviolet (FUV) radiation. Theoretical models
predict that this FUV radiation produces photo-dissociation regions (PDRs) on
the surfaces of protoplanetary disks around low-mass stars, impacting planet
formation within the disks. We report JWST and Atacama Large Millimetere Array
observations of a FUV-irradiated protoplanetary disk in the Orion Nebula.
Emission lines are detected from the PDR; modelling their kinematics and
excitation allows us to constrain the physical conditions within the gas. We
quantify the mass-loss rate induced by the FUV irradiation, finding it is
sufficient to remove gas from the disk in less than a million years. This is
rapid enough to affect giant planet formation in the disk
The James Webb Space Telescope Mission
Twenty-six years ago a small committee report, building on earlier studies,
expounded a compelling and poetic vision for the future of astronomy, calling
for an infrared-optimized space telescope with an aperture of at least .
With the support of their governments in the US, Europe, and Canada, 20,000
people realized that vision as the James Webb Space Telescope. A
generation of astronomers will celebrate their accomplishments for the life of
the mission, potentially as long as 20 years, and beyond. This report and the
scientific discoveries that follow are extended thank-you notes to the 20,000
team members. The telescope is working perfectly, with much better image
quality than expected. In this and accompanying papers, we give a brief
history, describe the observatory, outline its objectives and current observing
program, and discuss the inventions and people who made it possible. We cite
detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space
Telescope Overview, 29 pages, 4 figure
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