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We present a novel approach to voxelization, based on intersecting the input primitives against intersection targets in the voxel grid. Instead of relying on geometric proximity measures, our approach is topological in nature, i.e...
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We present a novel approach to voxelization, based on intersecting the input primitives against intersection targets in the voxel grid. Instead of relying on geometric proximity measures, our approach is topological in nature, i.e., it builds on the connectivity and separability properties of the input and the intersection targets. We discuss voxelization of curves and surfaces in both 2D and 3D, and derive intersection targets that produce voxelizations with various connectivity, separability and thinness properties. The simplicity of our method allows for easy proofs of these properties. Our approach is directly applicable to curved primitives, and it is independent of input tessellation.
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The efficient evaluation of visibility in a three-dimensional scene is a longstanding problem in computer graphics. Visibility evaluations come in many different forms: figuring out what object is visible in a pixel; determining w...
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The efficient evaluation of visibility in a three-dimensional scene is a longstanding problem in computer graphics. Visibility evaluations come in many different forms: figuring out what object is visible in a pixel; determining whether a point is visible to a light source; or evaluating the mutual visibility between 2 surface points. This paper provides a new, experimental view on visibility, based on a probabilistic evaluation of the visibility function. Instead of checking the visibility against all possible intervening geometry, the visibility between 2 points is now evaluated by testing only a random subset of objects. The result is not a Boolean value that is either 0 or 1, but a numerical value that can even be negative. Because we use the visibility evaluation as part of the integrand in illumination computations, the probabilistic evaluation of visibility becomes part of the Monte Carlo procedure of estimating the illumination integral, and results in an unbiased computation of illumination values in the scene. Moreover, the number of intersections tests for any given ray is decreased, since only a random selection of geometric primitives is tested. Although probabilistic visibility is an experimental and new idea, we present a practical algorithm for direct illumination that uses the probabilistic nature of visibility evaluations.
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Daniel (or Daan in Dutch) M. Kan was born on August 4,1927, and grew up as the only child in a liberal Jewish family in the southern quarter of Amsterdam, where his father worked as a lawyer. In 1939 he entered the Barlaeus Gymnas...
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Daniel (or Daan in Dutch) M. Kan was born on August 4,1927, and grew up as the only child in a liberal Jewish family in the southern quarter of Amsterdam, where his father worked as a lawyer. In 1939 he entered the Barlaeus Gymnasium, a secondary school in the center of Amsterdam, then and to this day one of the best schools in Amsterdam. He was only able to stay there for two years, because after the school year 1940-41, under German occupation Jewish children were no longer allowed at that school. Instead, he went to the Jewish Lyceum (Joods Iyceum).
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The purpose of open access (OA) is to make published research freely available to all.One of the pioneering OA publications has been New Journal of Physics (NJP), which was launched 10 years ago this month by the Institute of Phys...
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The purpose of open access (OA) is to make published research freely available to all.One of the pioneering OA publications has been New Journal of Physics (NJP), which was launched 10 years ago this month by the Institute of Physics and the German Physical Society (see pp12-13). Instead of charging for subscriptions, NJP and other journals like it levy a publication fee on authors, in return for which their papers are made available to all online free of charge.
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Wolfram, who is best known for creating theMathematica software package, was speakingat a demonstration last month of Wolfram Alpha —a new online service that answers factual queriesdirectly instead of listing webpages that could...
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Wolfram, who is best known for creating theMathematica software package, was speakingat a demonstration last month of Wolfram Alpha —a new online service that answers factual queriesdirectly instead of listing webpages that couldcontain the answer.
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As we move into the final months of the year, we can acknowledge the industry has been through a very trying period and there is probably more to come. Anxiety over a multitude of issues (not the least of which includes COVID-19, ...
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As we move into the final months of the year, we can acknowledge the industry has been through a very trying period and there is probably more to come. Anxiety over a multitude of issues (not the least of which includes COVID-19, a possible recession on the horizon, election issues and more) should not be what defines 2020. Instead, our responses should determine what comes next.
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Unmotivated to search for life on other worlds,Voltaire instead brought extraterrestrials to earth in Micromegas,a tale of cosmic perspective the French philosopher published in the middle of the eighteenth century.One of Voltaire...
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Unmotivated to search for life on other worlds,Voltaire instead brought extraterrestrials to earth in Micromegas,a tale of cosmic perspective the French philosopher published in the middle of the eighteenth century.One of Voltaire's aliens is from Sirius and is 24 miles tall.His traveling companion lives on Saturn and is only a little over a mile in height.Their size makes it difficult for them to detect life on earth,and they conclude there is none.Then they fabricate a giant magnifying glass that allows them to discern a whale,a ship,and people.At first misled,they conclude the people are too tiny to possess intelligence,but they eventually manage to find a way to communicate with the human specks and realize intelligence,of a sort,inhabits the planet.
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Sorting of glycosylphosphatidyl-inositol-anchored proteins (GPI-APs) in polarized epithelial cells is not fully understood. Oligomerization in the Golgi complex has emerged as the crucial event driving apical segregation of GPI-AP...
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Sorting of glycosylphosphatidyl-inositol-anchored proteins (GPI-APs) in polarized epithelial cells is not fully understood. Oligomerization in the Golgi complex has emerged as the crucial event driving apical segregation of GPI-APs in two different kind of epithelial cells, Madin-Darby canine kidney (MDCK) and Fisher rat thyroid (FRT) cells, but whether the mechanism is conserved is unknown. In MDCK cells cholesterol promotes GPI-AP oligomerization, as well as apical sorting of GPI-APs. Here we show that FRT cells lack this cholesterol-driven oligomerization as apical sorting mechanism. In these cells both apical and basolateral GPI-APs display restricted diffusion in the Golgi likely due to a cholesterol-enriched membrane environment. It is striking that N-glycosylation is the critical event for oligomerization and apical sorting of GPI-APs in FRT cells but not in MDCK cells. Our data indicate that at least two mechanisms exist to determine oligomerization in the Golgi leading to apical sorting of GPI-APs. One depends on cholesterol, and the other depends on N-glycosylation and is insensitive to cholesterol addition or depletion.
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Networks in nature do not act in isolation, but instead exchange information and depend on one another to function properly1-3. Theory has shown that connecting random networks may very easily result in abrupt failures3-6. This fi...
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Networks in nature do not act in isolation, but instead exchange information and depend on one another to function properly1-3. Theory has shown that connecting random networks may very easily result in abrupt failures3-6. This finding reveals an intriguing paradox7,8:if natural systems organize in interconnected networks, how can they be so stable? Here we provide a solution to this conundrum, showing that the stability of a system of networks relies on the relation between the internal structure of a network and its pattern of connections to other networks. Specifically,we demonstrate that if interconnections are provided by network hubs, and the connections between networks are moderately convergent, the systemof networks is stable and robust to failure.We test this theoretical prediction on two independent experiments of functional brain networks (in task and resting states), which showthat brain networks are connected with a topology that maximizes stability according to the theory.
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The experimental proof of the possibility of the formation of an open sector instead of a twin boundary in pentagonal small particles, which was previously regarded in the literature as an improbable channel of relaxation of the e...
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The experimental proof of the possibility of the formation of an open sector instead of a twin boundary in pentagonal small particles, which was previously regarded in the literature as an improbable channel of relaxation of the elastic stress associated with a disclination defect, is presented. The relation between the critical size of the pentagonal small particle and the sector angle at which the probability of this channel of elastic stress relaxation becomes considerable is discussed.
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