1,929 research outputs found
Studying and solving visual artifacts occurring when procedural texturing with paradoxical requirements
International audienceTextures are images widely used by computer graphics artists to add visual detail to their work. Textures may come from different sources, such as pictures of real-world surfaces, manually created images using graphics editors, or algorithmic processes. âProcedural texturingâ refers to the creation of textures using algorithmic processes.Procedural textures offer many advantages, including the ability to manipulate their appearance through parameters. Many applications rely on changing those parameters to evolve the look of those textures over time or space. This often introduces requirements contradictory with the structure of the unaltered texture, often resulting in visible rendering artifacts. As an example, to animate a lava flow the rendered texture should be an effective representation of the simulated flow, but features such as rocks floating over should not be distorted, nor brutally appearor disappear thus disrupting the illusion. Informally, we want our lava texture to âchange, but stay the sameâ. This example is an instance of the consistency problem that arises when changing parameters of a texture, resulting in noticeable artifacts in the rendered result.In this project, we seek to classify these artifacts depending on their causes and their effects on textures, but also how we can objectively detect and explain their presence, and so predict their occurrence. Analytical and statistical analysis of procedural texturing processes will be performed, in order to find the relation with the corresponding artifacts.Les textures sont des images largement utilisĂ©es par les artistes infographistes pour ajouter des dĂ©tails dans leurs rendus. Ces textures peuvent provenir de diffĂ©rentes sources, telles que des images de surfaces rĂ©elles, des images crĂ©Ă©es manuellement dans des logiciels, ou des processus algorithmiques. Ces derniĂšres sont appelĂ©esâtextures procĂ©duralesâ.Les textures procĂ©durales offrent beaucoup dâavantages, notamment la possibilitĂ© de dĂ©finir leur apparence Ă partir de paramĂštres. Dans de nombreuses situations, ces paramĂštres Ă©voluent au cours du temps ou dans lâespace. Cela introduit cependant des contraintes contradictoires Ă lâapparence de la texture originale, introduisant ainsi des artefacts visibles. Par exemple, pour animer un flot de lave, la texture rendue devrait suivre le flot simulĂ©, mais les formes telles que des rochers flottants Ă la surface ne devraient pas ĂȘtre distordus, ni apparaĂźtre ou disparaĂźtrebrutalement, ce qui casserait lâillusion. Informellement, cette texture de lave doit âchanger, mais rester la mĂȘmeâ. Cet exemple est une instance du problĂšme de la cohĂ©rence temporelle liĂ© Ă lâĂ©volution de paramĂštres dâune texture, ce qui introduit des artefacts dans le rendu final.Au cours de ce projet, nous essayons de classer les diffĂ©rents artefacts selon les causes qui les produisent et leurs effets sur les textures. Nous cherchons aussi des mĂ©thodes pour dĂ©crire objectivement et dĂ©tecter leur prĂ©sence, et mĂȘme prĂ©dire leur apparition. Des mĂ©thodes analytiques mais aussi statistiques des procĂ©dĂ©s de texture vont ĂȘtre mis en Ćuvre, afin de trouver les liens entre artefacts et descripteurs
Making Gabor Noise Fast and Normalized
International audienceGabor Noise is a powerful procedural texture synthesis technique, but it has two major drawbacks: It is costly due to the high required splat density and not always predictable because properties of instances can differ from those of the process. We bench performance and quality using alternatives for each Gabor Noise ingredient: point distribution, kernel weighting and kernel shape. For this, we introduce 3 objective criteria to measure process convergence, process stationarity, and instance stationarity. We show that minor implementation changes allow for 17-24x speed-up with same or better quality
Gabor Noise revisité
International audienceGabor noise ingredients â points distribution, weights, kernel â can be changed. We show that minor implementation changes allow for huge 17 â 24Ă speed-up with same or better quality.Les ingrĂ©dients du Gabor noise â distribution de points, poids, kernel â peuvent ĂȘtre changĂ©s. Nous montrons que des modifications mineurs de l'implĂ©mentation permettent des gains en performance entre 17 et 24 fois tout en maintenant voire amĂ©liorant la qualitĂ© du rĂ©sultat
Septic cardiomyopathy
Depression of left ventricular (LV) intrinsic contractility is constant in patients with septic shock. Because most parameters of cardiac function are strongly dependent on afterload, especially in this context, the cardiac performance evaluated at the bedside reflects intrinsic contractility, but also the degree of vasoplegia. Recent advances in echocardiography have allowed better characterization of septic cardiomyopathy. It is always reversible providing the patient's recovery. Unlike classic cardiomyopathy, it is not associated with high filling pressures, for two reasons: improvement in LV compliance and associated right ventricular dysfunction. Although, it is unclear to which extent it affects prognosis, a hyperkinetic state is indicative of a profound and persistent vasoplegia associated with a high mortality rate. Preliminary data suggest that the hemodynamic response to a dobutamine challenge has a prognostic value, but large studies are required to establish whether inotropic drugs should be used to treat this septic cardiac dysfunction
Recommended from our members
Host-pathogen interactome mapping for HTLV-1 and -2 retroviruses
Human T-cell leukemia virus type 1 (HTLV-1) and type 2 both target T lymphocytes, yet induce radically different phenotypic outcomes. HTLV-1 is a causative agent of Adult T-cell leukemia (ATL), whereas HTLV-2, highly similar to HTLV-1, causes no known overt disease. HTLV gene products are engaged in a dynamic struggle of activating and antagonistic interactions with host cells. Investigations focused on one or a few genes have identified several human factors interacting with HTLV viral proteins. Most of the available interaction data concern the highly investigated HTLV-1 Tax protein. Identifying shared and distinct host-pathogen protein interaction profiles for these two viruses would enlighten how they exploit distinctive or common strategies to subvert cellular pathways toward disease progression.Comparative StudyJournal ArticleResearch Support, N.I.H. ExtramuralResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe
Detailed spectral and morphological analysis of the shell type SNR RCW 86
Aims: We aim for an understanding of the morphological and spectral
properties of the supernova remnant RCW~86 and for insights into the production
mechanism leading to the RCW~86 very high-energy gamma-ray emission. Methods:
We analyzed High Energy Spectroscopic System data that had increased
sensitivity compared to the observations presented in the RCW~86 H.E.S.S.
discovery publication. Studies of the morphological correlation between the
0.5-1~keV X-ray band, the 2-5~keV X-ray band, radio, and gamma-ray emissions
have been performed as well as broadband modeling of the spectral energy
distribution with two different emission models. Results:We present the first
conclusive evidence that the TeV gamma-ray emission region is shell-like based
on our morphological studies. The comparison with 2-5~keV X-ray data reveals a
correlation with the 0.4-50~TeV gamma-ray emission.The spectrum of RCW~86 is
best described by a power law with an exponential cutoff at TeV and a spectral index of ~. A static
leptonic one-zone model adequately describes the measured spectral energy
distribution of RCW~86, with the resultant total kinetic energy of the
electrons above 1 GeV being equivalent to 0.1\% of the initial kinetic
energy of a Type I a supernova explosion. When using a hadronic model, a
magnetic field of ~100G is needed to represent the measured data.
Although this is comparable to formerly published estimates, a standard
E spectrum for the proton distribution cannot describe the gamma-ray
data. Instead, a spectral index of ~1.7 would be required, which
implies that ~erg has been transferred into
high-energy protons with the effective density cm^-3. This
is about 10\% of the kinetic energy of a typical Type Ia supernova under the
assumption of a density of 1~cm^-3.Comment: accepted for publication by A&
Characterizing the gamma-ray long-term variability of PKS 2155-304 with H.E.S.S. and Fermi-LAT
Studying the temporal variability of BL Lac objects at the highest energies
provides unique insights into the extreme physical processes occurring in
relativistic jets and in the vicinity of super-massive black holes. To this
end, the long-term variability of the BL Lac object PKS 2155-304 is analyzed in
the high (HE, 100 MeV 200 GeV)
gamma-ray domain. Over the course of ~9 yr of H.E.S.S observations the VHE
light curve in the quiescent state is consistent with a log-normal behavior.
The VHE variability in this state is well described by flicker noise
(power-spectral-density index {\ss}_VHE = 1.10 +0.10 -0.13) on time scales
larger than one day. An analysis of 5.5 yr of HE Fermi LAT data gives
consistent results ({\ss}_HE = 1.20 +0.21 -0.23, on time scales larger than 10
days) compatible with the VHE findings. The HE and VHE power spectral densities
show a scale invariance across the probed time ranges. A direct linear
correlation between the VHE and HE fluxes could neither be excluded nor firmly
established. These long-term-variability properties are discussed and compared
to the red noise behavior ({\ss} ~ 2) seen on shorter time scales during
VHE-flaring states. The difference in power spectral noise behavior at VHE
energies during quiescent and flaring states provides evidence that these
states are influenced by different physical processes, while the compatibility
of the HE and VHE long-term results is suggestive of a common physical link as
it might be introduced by an underlying jet-disk connection.Comment: 11 pages, 16 figure
Detection of variable VHE gamma-ray emission from the extra-galactic gamma-ray binary LMC P3
Context. Recently, the high-energy (HE, 0.1-100 GeV) -ray emission
from the object LMC P3 in the Large Magellanic Cloud (LMC) has been discovered
to be modulated with a 10.3-day period, making it the first extra-galactic
-ray binary.
Aims. This work aims at the detection of very-high-energy (VHE, >100 GeV)
-ray emission and the search for modulation of the VHE signal with the
orbital period of the binary system.
Methods. LMC P3 has been observed with the High Energy Stereoscopic System
(H.E.S.S.); the acceptance-corrected exposure time is 100 h. The data set has
been folded with the known orbital period of the system in order to test for
variability of the emission. Energy spectra are obtained for the orbit-averaged
data set, and for the orbital phase bin around the VHE maximum.
Results. VHE -ray emission is detected with a statistical
significance of 6.4 . The data clearly show variability which is
phase-locked to the orbital period of the system. Periodicity cannot be deduced
from the H.E.S.S. data set alone. The orbit-averaged luminosity in the
TeV energy range is erg/s. A luminosity of erg/s is reached during 20% of the orbit. HE and VHE
-ray emissions are anti-correlated. LMC P3 is the most luminous
-ray binary known so far.Comment: 5 pages, 3 figures, 1 table, accepted for publication in A&
The exceptionally powerful TeV gamma-ray emitters in the Large Magellanic Cloud
The Large Magellanic Cloud, a satellite galaxy of the Milky Way, has been
observed with the High Energy Stereoscopic System (H.E.S.S.) above an energy of
100 billion electron volts for a deep exposure of 210 hours. Three sources of
different types were detected: the pulsar wind nebula of the most energetic
pulsar known N 157B, the radio-loud supernova remnant N 132D and the largest
non-thermal X-ray shell - the superbubble 30 Dor C. The unique object SN 1987A
is, surprisingly, not detected, which constrains the theoretical framework of
particle acceleration in very young supernova remnants. These detections reveal
the most energetic tip of a gamma-ray source population in an external galaxy,
and provide via 30 Dor C the unambiguous detection of gamma-ray emission from a
superbubble.Comment: Published in Science Magazine (Jan. 23, 2015). This ArXiv version has
the supplementary online material incorporated as an appendix to the main
pape
Prediction of arterial pressure increase after fluid challenge
<p>Abstract</p> <p>Background</p> <p>Mean arterial pressure above 65 mmHg is recommended for critically ill hypotensive patients whereas they do not benefit from supranormal cardiac output values. In this study we investigated if the increase of mean arterial pressure after volume expansion could be predicted by cardiovascular and renal variables. This is a relevant topic because unnecessary positive fluid balance increases mortality, organ dysfunction and Intensive Care Unit length of stay.</p> <p>Methods</p> <p>Thirty-six hypotensive patients (mean arterial pressure < 65 mmH) received a fluid challenge with hydroxyethyl starch. Patients were excluded if they had active bleeding and/or required changes in vasoactive agents infusion rate in the previous 30 minutes. Responders were defined by the increase of mean arterial pressure value to over 65 mmHg or by more than 20% with respect to the value recorded before fluid challenge. Measurements were performed before and at one hour after the end of fluid challenge.</p> <p>Results</p> <p>Twenty-two patients (61%) increased arterial pressure after volume expansion. Baseline heart rate, arterial pressure, central venous pressure, central venous saturation, central venous to arterial PCO<sub>2 </sub>difference, lactate, urinary output, fractional excretion of sodium and urinary sodium/potassium ratio were similar between responder and non-responder. Only 7 out of 36 patients had valuable dynamic indices and then we excluded them from analysis. When the variables were tested as predictors of responders, they showed values of areas under the ROC curve ranging between 0.502 and 0.604. Logistic regression did not reveal any association between variables and responder definition.</p> <p>Conclusions</p> <p>Fluid challenge did not improve arterial pressure in about one third of hypotensive critically ill patients. Cardiovascular and renal variables did not enable us to predict the individual response to volume administration.</p> <p>Trial registration</p> <p>ClinicalTrials.gov: <a href="http://www.clinicaltrials.gov/ct2/show/NCT00721604">NCT00721604</a>.</p
- âŠ