56,522 research outputs found
3D Visibility Representations of 1-planar Graphs
We prove that every 1-planar graph G has a z-parallel visibility
representation, i.e., a 3D visibility representation in which the vertices are
isothetic disjoint rectangles parallel to the xy-plane, and the edges are
unobstructed z-parallel visibilities between pairs of rectangles. In addition,
the constructed representation is such that there is a plane that intersects
all the rectangles, and this intersection defines a bar 1-visibility
representation of G.Comment: Appears in the Proceedings of the 25th International Symposium on
Graph Drawing and Network Visualization (GD 2017
Visibility Constrained Generative Model for Depth-based 3D Facial Pose Tracking
In this paper, we propose a generative framework that unifies depth-based 3D
facial pose tracking and face model adaptation on-the-fly, in the unconstrained
scenarios with heavy occlusions and arbitrary facial expression variations.
Specifically, we introduce a statistical 3D morphable model that flexibly
describes the distribution of points on the surface of the face model, with an
efficient switchable online adaptation that gradually captures the identity of
the tracked subject and rapidly constructs a suitable face model when the
subject changes. Moreover, unlike prior art that employed ICP-based facial pose
estimation, to improve robustness to occlusions, we propose a ray visibility
constraint that regularizes the pose based on the face model's visibility with
respect to the input point cloud. Ablation studies and experimental results on
Biwi and ICT-3DHP datasets demonstrate that the proposed framework is effective
and outperforms completing state-of-the-art depth-based methods
Three-dimensional hydrodynamical simulations of red giant stars: semi-global models for the interpretation of interferometric observations
Context. Theoretical predictions from models of red giant branch stars are a
valuable tool for various applications in astrophysics ranging from galactic
chemical evolution to studies of exoplanetary systems. Aims. We use the
radiative transfer code OPTIM3D and realistic 3D radiative-hydrodynamical (RHD)
surface convection simulations of red giants to explore the impact of
granulation on interferometric observables. Methods. We compute intensity maps
for the 3D simulation snapshots in two filters: in the optical at 5000 \pm 300
{\AA} and in the K band 2.14 0.26 {\mu}m FLUOR filter, corresponding to
the wavelength-range of instruments mounted on the CHARA interferometer. From
the intensity maps, we construct images of the stellar disks, accounting for
center-to-limb variations. We then derive interferometric visibility amplitudes
and phases. We study their behavior with position angle and wavelength.
Results. We provide average limb-darkening coefficients for different
metallicities and wavelength-ranges. We detail the prospects for the detection
and characterization of granulation and center-to-limb variations of red giant
stars with today's interferometers. We find that the effect of
convective-related surface structures depends on metallicity and surface
gravity. We provided theoretical closure phases that should be incorporated
into the analysis of red giant planet companion closure phase signals. We
estimate 3D-1D corrections to stellar radii determination: 3D models are ~ 3.5%
smaller to ~ 1% larger in the optical with respect to 1D, and roughly 0.5 to
1.5% smaller in the infrared. Even if these corrections are small, they are
important to properly set the zero point of effective temperature scale derived
by interferometry and to strengthen the confidence of existing red giant
catalogues of calibrating stars for interferometry.Comment: Accepted for publication on Astronomy & Astrophysics, 14 pages, 13
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Search-based 3D Planning and Trajectory Optimization for Safe Micro Aerial Vehicle Flight Under Sensor Visibility Constraints
Safe navigation of Micro Aerial Vehicles (MAVs) requires not only
obstacle-free flight paths according to a static environment map, but also the
perception of and reaction to previously unknown and dynamic objects. This
implies that the onboard sensors cover the current flight direction. Due to the
limited payload of MAVs, full sensor coverage of the environment has to be
traded off with flight time. Thus, often only a part of the environment is
covered.
We present a combined allocentric complete planning and trajectory
optimization approach taking these sensor visibility constraints into account.
The optimized trajectories yield flight paths within the apex angle of a
Velodyne Puck Lite 3D laser scanner enabling low-level collision avoidance to
perceive obstacles in the flight direction. Furthermore, the optimized
trajectories take the flight dynamics into account and contain the velocities
and accelerations along the path.
We evaluate our approach with a DJI Matrice 600 MAV and in simulation
employing hardware-in-the-loop.Comment: In Proceedings of IEEE International Conference on Robotics and
Automation (ICRA), Montreal, Canada, May 201
Occlusion Handling using Semantic Segmentation and Visibility-Based Rendering for Mixed Reality
Real-time occlusion handling is a major problem in outdoor mixed reality
system because it requires great computational cost mainly due to the
complexity of the scene. Using only segmentation, it is difficult to accurately
render a virtual object occluded by complex objects such as trees, bushes etc.
In this paper, we propose a novel occlusion handling method for real-time,
outdoor, and omni-directional mixed reality system using only the information
from a monocular image sequence. We first present a semantic segmentation
scheme for predicting the amount of visibility for different type of objects in
the scene. We also simultaneously calculate a foreground probability map using
depth estimation derived from optical flow. Finally, we combine the
segmentation result and the probability map to render the computer generated
object and the real scene using a visibility-based rendering method. Our
results show great improvement in handling occlusions compared to existing
blending based methods
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