17,114 research outputs found
Revolvable Indoor Panoramas Using a Rectified Azimuthal Projection
We present an algorithm for converting an indoor spherical panorama into a
photograph with a simulated overhead view. The resulting image will have an
extremely wide field of view covering up to 4{\pi} steradians of the spherical
panorama. We argue that our method complements the stereographic projection
commonly used in the "little planet" effect. The stereographic projection works
well in creating little planets of outdoor scenes; whereas our method is a
well-suited counterpart for indoor scenes. The main innovation of our method is
the introduction of a novel azimuthal map projection that can smoothly blend
between the stereographic projection and the Lambert azimuthal equal-area
projection. Our projection has an adjustable parameter that allows one to
control and compromise between distortions in shape and distortions in size
within the projected panorama. This extra control parameter gives our
projection the ability to produce superior results over the stereographic
projection.Comment: expanded version of "An Indoor Alternative to Stereographic Spherical
Panoramas" (Bridges 2014
Recommended from our members
Adaptive Composite Map Projections
This is the author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by IEEE-Institute of Electrical and Electronics Engineers and can be found at: http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=2945. ©2012 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.All major web mapping services use the web Mercator projection. This is a poor choice for maps of the entire globe or\ud
areas of the size of continents or larger countries because the Mercator projection shows medium and higher latitudes with extreme\ud
areal distortion and provides an erroneous impression of distances and relative areas. The web Mercator projection is also not able\ud
to show the entire globe, as polar latitudes cannot be mapped. When selecting an alternative projection for information visualization,\ud
rivaling factors have to be taken into account, such as map scale, the geographic area shown, the map’s height-to-width ratio, and\ud
the type of cartographic visualization. It is impossible for a single map projection to meet the requirements for all these factors. The\ud
proposed composite map projection combines several projections that are recommended in cartographic literature and seamlessly\ud
morphs map space as the user changes map scale or the geographic region displayed. The composite projection adapts the map’s\ud
geometry to scale, to the map’s height-to-width ratio, and to the central latitude of the displayed area by replacing projections and\ud
adjusting their parameters. The composite projection shows the entire globe including poles; it portrays continents or larger\ud
countries with less distortion (optionally without areal distortion); and it can morph to the web Mercator projection for maps showing\ud
small regions
LMap: Shape-Preserving Local Mappings for Biomedical Visualization
Visualization of medical organs and biological structures is a challenging
task because of their complex geometry and the resultant occlusions. Global
spherical and planar mapping techniques simplify the complex geometry and
resolve the occlusions to aid in visualization. However, while resolving the
occlusions these techniques do not preserve the geometric context, making them
less suitable for mission-critical biomedical visualization tasks. In this
paper, we present a shape-preserving local mapping technique for resolving
occlusions locally while preserving the overall geometric context. More
specifically, we present a novel visualization algorithm, LMap, for conformally
parameterizing and deforming a selected local region-of-interest (ROI) on an
arbitrary surface. The resultant shape-preserving local mappings help to
visualize complex surfaces while preserving the overall geometric context. The
algorithm is based on the robust and efficient extrinsic Ricci flow technique,
and uses the dynamic Ricci flow algorithm to guarantee the existence of a local
map for a selected ROI on an arbitrary surface. We show the effectiveness and
efficacy of our method in three challenging use cases: (1) multimodal brain
visualization, (2) optimal coverage of virtual colonoscopy centerline
flythrough, and (3) molecular surface visualization.Comment: IEEE Transactions on Visualization and Computer Graphics, 24(12):
3111-3122, 2018 (12 pages, 11 figures
Fast Disk Conformal Parameterization of Simply-connected Open Surfaces
Surface parameterizations have been widely used in computer graphics and
geometry processing. In particular, as simply-connected open surfaces are
conformally equivalent to the unit disk, it is desirable to compute the disk
conformal parameterizations of the surfaces. In this paper, we propose a novel
algorithm for the conformal parameterization of a simply-connected open surface
onto the unit disk, which significantly speeds up the computation, enhances the
conformality and stability, and guarantees the bijectivity. The conformality
distortions at the inner region and on the boundary are corrected by two steps,
with the aid of an iterative scheme using quasi-conformal theories.
Experimental results demonstrate the effectiveness of our proposed method
Non-Linear Phase-Shifting of Haar Wavelets for Run-Time All-Frequency Lighting
This paper focuses on real-time all-frequency image-based rendering using an
innovative solution for run-time computation of light transport. The approach
is based on new results derived for non-linear phase shifting in the Haar
wavelet domain. Although image-based methods for real-time rendering of dynamic
glossy objects have been proposed, they do not truly scale to all possible
frequencies and high sampling rates without trading storage, glossiness, or
computational time, while varying both lighting and viewpoint. This is due to
the fact that current approaches are limited to precomputed radiance transfer
(PRT), which is prohibitively expensive in terms of memory requirements and
real-time rendering when both varying light and viewpoint changes are required
together with high sampling rates for high frequency lighting of glossy
material. On the other hand, current methods cannot handle object rotation,
which is one of the paramount issues for all PRT methods using wavelets. This
latter problem arises because the precomputed data are defined in a global
coordinate system and encoded in the wavelet domain, while the object is
rotated in a local coordinate system. At the root of all the above problems is
the lack of efficient run-time solution to the nontrivial problem of rotating
wavelets (a non-linear phase-shift), which we solve in this paper
Deep Lighting Environment Map Estimation from Spherical Panoramas
Estimating a scene's lighting is a very important task when compositing
synthetic content within real environments, with applications in mixed reality
and post-production. In this work we present a data-driven model that estimates
an HDR lighting environment map from a single LDR monocular spherical panorama.
In addition to being a challenging and ill-posed problem, the lighting
estimation task also suffers from a lack of facile illumination ground truth
data, a fact that hinders the applicability of data-driven methods. We approach
this problem differently, exploiting the availability of surface geometry to
employ image-based relighting as a data generator and supervision mechanism.
This relies on a global Lambertian assumption that helps us overcome issues
related to pre-baked lighting. We relight our training data and complement the
model's supervision with a photometric loss, enabled by a differentiable
image-based relighting technique. Finally, since we predict spherical spectral
coefficients, we show that by imposing a distribution prior on the predicted
coefficients, we can greatly boost performance. Code and models available at
https://vcl3d.github.io/DeepPanoramaLighting.Comment: Code and models available at
https://vcl3d.github.io/DeepPanoramaLightin
OmniDepth: Dense Depth Estimation for Indoors Spherical Panoramas
Recent work on depth estimation up to now has only focused on projective
images ignoring 360 content which is now increasingly and more easily produced.
We show that monocular depth estimation models trained on traditional images
produce sub-optimal results on omnidirectional images, showcasing the need for
training directly on 360 datasets, which however, are hard to acquire. In this
work, we circumvent the challenges associated with acquiring high quality 360
datasets with ground truth depth annotations, by re-using recently released
large scale 3D datasets and re-purposing them to 360 via rendering. This
dataset, which is considerably larger than similar projective datasets, is
publicly offered to the community to enable future research in this direction.
We use this dataset to learn in an end-to-end fashion the task of depth
estimation from 360 images. We show promising results in our synthesized data
as well as in unseen realistic images.Comment: Pre-print to appear in ECCV1
Compactified Cosmological Simulations of the Infinite Universe
We present a novel -body simulation method that compactifies the infinite
spatial extent of the Universe into a finite sphere with isotropic boundary
conditions to follow the evolution of the large-scale structure. Our approach
eliminates the need for periodic boundary conditions, a mere numerical
convenience which is not supported by observation and which modifies the law of
force on large scales in an unrealistic fashion. We demonstrate that our method
outclasses standard simulations executed on workstation-scale hardware in
dynamic range, it is balanced in following a comparable number of high and low
modes and, its fundamental geometry and topology match observations. Our
approach is also capable of simulating an expanding, infinite universe in
static coordinates with Newtonian dynamics. The price of these achievements is
that most of the simulated volume has smoothly varying mass and spatial
resolution, an approximation that carries different systematics than periodic
simulations.
Our initial implementation of the method is called StePS which stands for
Stereographically Projected Cosmological Simulations. It uses stereographic
projection for space compactification and naive force
calculation which is nevertheless faster to arrive at a correlation function of
the same quality than any standard (tree or PM) algorithm with similar
spatial and mass resolution. The force calculation is easy to adapt to
modern graphics cards, hence our code can function as a high-speed prediction
tool for modern large-scale surveys. To learn about the limits of the
respective methods, we compare StePS with GADGET-2
\citep{Gadget2_2005MNRAS.364.1105S} running matching initial conditions
Warping Peirce Quincuncial Panoramas
The Peirce quincuncial projection is a mapping of the surface of a sphere to
the interior of a square. It is a conformal map except for four points on the
equator. These points of non-conformality cause significant artifacts in
photographic applications. In this paper, we propose an algorithm and
user-interface to mitigate these artifacts. Moreover, in order to facilitate an
interactive user-interface, we present a fast algorithm for calculating the
Peirce quincuncial projection of spherical imagery. We then promote the Peirce
quincuncial projection as a viable alternative to the more popular
stereographic projection in some scenarios.Comment: updated source code with figures and explanation of the software
implementatio
Measuring the Effects of Scalar and Spherical Colormaps on Ensembles of DMRI Tubes
We report empirical study results on the color encoding of ensemble scalar
and orientation to visualize diffusion magnetic resonance imaging (DMRI) tubes.
The experiment tested six scalar colormaps for average fractional anisotropy
(FA) tasks (grayscale, blackbody, diverging, isoluminant-rainbow,
extended-blackbody, and coolwarm) and four three-dimensional (3D) directional
encodings for tract tracing tasks (uniform gray, absolute, eigenmap, and Boy's
surface embedding). We found that extended-blackbody, coolwarm, and blackbody
remain the best three approaches for identifying ensemble average in 3D.
Isoluminant-rainbow coloring led to the same ensemble mean accuracy as other
colormaps. However, more than 50% of the answers consistently had higher
estimates of the ensemble average, independent of the mean values. Hue, not
luminance, influences ensemble estimates of mean values. For ensemble
orientation-tracing tasks, we found that the Boy's surface embedding (greatest
spatial resolution and contrast) and absolute color (lowest spatial resolution
and contrast) schemes led to more accurate answers than the eigenmaps scheme
(medium resolution and contrast), acting as the uncanny-valley phenomenon of
visualization design in terms of accuracy
- …