The Experts below are selected from a list of 4158 Experts worldwide ranked by ideXlab platform
Kenneth I. Joy - One of the best experts on this subject based on the ideXlab platform.
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compression and occlusion culling for fast isosurface extraction from massive datasets
Mathematical Foundations of Scientific Visualization Computer Graphics and Massive Data Exploration, 2009Co-Authors: Benjamin F Gregorski, J Senecal, Mark A Duchaineau, Kenneth I. JoyAbstract:We present two algorithms for data compression and occlusion culling that im- prove interactive, adaptive isosurface extraction from large volume datasets. Our algorithm, based on hierarchical tetrahedral meshes defined by longest edge bisection, allows arbitrary Isosurfaces to be adaptively extracted at interactive rates from losslessly compressed volumes where the region of interest, determined at runtime by user interaction, is decompressed on- the-fly. For interactive applications, we exploit frame-to-frame coherence between consecutive views to simplify the mesh structure in occluded regions and eliminate occluded triangles sig- nificantly reducing the complexity of the visualized surface and the underlying multiresolution volume representation. We extend the use of hardware accelerated occlusion queries to adap- tive isosurface extraction applications where the surface geometry and topology change with the level-of-detail and view-point and the user can select an arbitrary isovalue for visualization.
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extracting geometrically continuous Isosurfaces from adaptive mesh refinement data
2004Co-Authors: David Fang, Bernd Hamann, Gunther H Weber, Hank Childs, Eric Brugger, Kenneth I. JoyAbstract:Author(s): Fang, David; Weber, Gunther H.; Childs, Hank; Brugger, Eric S.; Hamann, Bernd; Joy, Ken | Abstract: We present a method for avoiding cracks in Isosurfaces extracted from adaptive mesh refinement (AMR) data. By combining several rectilinear grids of different resolution, AMR methods substantially reduce storage and computation requirements to accurately represent and simulate complicated data and phenomena. AMR data consist of grids of different resolution. As a result discontinuities (''hanging nodes'') arise in dependent field variables at the interfaces of different resolution mesh elements. These discontinuities can result in cracks in Isosurfaces extracted for a specific value of a dependent scalar variable. We describe a method for creating transition regions'' between grids of different resolution. These regions are composed of pyramid elements that allow us to avoid crack formation during isosurface extraction.
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Adaptive extraction of time-varying Isosurfaces
IEEE transactions on visualization and computer graphics, 2004Co-Authors: Benjamin F Gregorski, Mark A Duchaineau, J.g. Senecal, Kenneth I. JoyAbstract:We present an algorithm for adaptively extracting and rendering Isosurfaces from compressed time-varying volume data sets. Tetrahedral meshes defined by longest edge bisection are used to create a multiresolution representation of the volume in the spatial domain that is adapted overtime to approximate the time-varying volume. The reextraction of the isosurface at each time step is accelerated with the vertex programming capabilities of modern graphics hardware. A data layout scheme which follows the access pattern indicated by mesh refinement is used to access the volume in a spatially and temporally coherent manner. This data layout scheme allows our algorithm to be used for out-of-core visualization.
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iso splatting a point based alternative to isosurface visualization
Pacific Conference on Computer Graphics and Applications, 2003Co-Authors: Bernd Hamann, Kenneth I. JoyAbstract:We present a new approach to isosurface visualization that we call "iso-splatting." We use point primitives for representing and rendering Isosurfaces. The method consists of two steps. In the first step, point samples are generated throughout the volumetric domain of a scalar function. In the second step, these points are projected onto the isosurface of interest. We render the resulting point set using a surface splatting algorithm. The method can be extended to out-of-core or parallel environments. Our results show that this method can offer much greater time and space efficiency when compared with standard triangle-based methods, thereby supporting higher levels of interactivity. Parts of the algorithm can be accelerated using graphics hardware. One key advantage of this approach is that, since extraction computations are divided into two smaller phases, work can be distributed to exploit all available resources.
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Hierarchical Isosurface Segmentation Based on Discrete Curvature
2003Co-Authors: Fabien Vivodtzev, Bernd Hamann, Lars Linsen, Kenneth I. Joy, Georges-pierre Bonneau, Bruno A. OlshausenAbstract:A high-level approach to describe the characteristics of a surface is to segment it into regions of uniform curvature behavior and construct an abstract representation given by a (topology) graph. We propose a surface segmentation method based on discrete mean and Gaussian curvature estimates. The surfaces are obtained from three-dimensional imaging data sets by isosurface extraction after data presmoothing and postprocessing the Isosurfaces by a surface-growing algorithm. We generate a hierarchical multiresolution representation of the isosurface. Segmentation and graph generation algorithms can be performed at various levels of detail. At a coarse level of detail, the algorithm detects the main features of the surface. This low-resolution description is used to determine constraints for the segmentation and graph generation at the higher resolutions. We have applied our methods to MRI data sets of human brains. The hierarchical segmentation framework can be used for brainmapping purposes.
Rudiger Westermann - One of the best experts on this subject based on the ideXlab platform.
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volumetric isosurface rendering with deep learning based super resolution
IEEE Transactions on Visualization and Computer Graphics, 2019Co-Authors: Sebastian Weiss, Mengyu Chu, Nils Thuerey, Rudiger WestermannAbstract:Rendering an accurate image of an isosurface in a volumetric field typically requires large numbers of data samples. Reducing this number lies at the core of research in volume rendering. With the advent of deep learning networks, a number of architectures have been proposed recently to infer missing samples in multi-dimensional fields, for applications such as image super-resolution. In this paper, we investigate the use of such architectures for learning the upscaling of a low-resolution sampling of an isosurface to a higher resolution, with reconstruction of spatial detail and shading. We introduce a fully convolutional neural network, to learn a latent representation generating smooth, edge-aware depth and normal fields as well as ambient occlusions from a low-resolution depth and normal field. By adding a frame-to-frame motion loss into the learning stage, upscaling can consider temporal variations and achieves improved frame-to-frame coherence. We assess the quality of inferred results and compare it to bi-linear and -cubic upscaling. We do this for Isosurfaces which were never seen during training, and investigate the improvements when the network can train on the same or similar Isosurfaces. We discuss remote visualization and foveated rendering as potential applications.
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volumetric isosurface rendering with deep learning based super resolution
arXiv: Graphics, 2019Co-Authors: Sebastian Weiss, Mengyu Chu, Nils Thuerey, Rudiger WestermannAbstract:Rendering an accurate image of an isosurface in a volumetric field typically requires large numbers of data samples. Reducing the number of required samples lies at the core of research in volume rendering. With the advent of deep learning networks, a number of architectures have been proposed recently to infer missing samples in multi-dimensional fields, for applications such as image super-resolution and scan completion. In this paper, we investigate the use of such architectures for learning the upscaling of a low-resolution sampling of an isosurface to a higher resolution, with high fidelity reconstruction of spatial detail and shading. We introduce a fully convolutional neural network, to learn a latent representation generating a smooth, edge-aware normal field and ambient occlusions from a low-resolution normal and depth field. By adding a frame-to-frame motion loss into the learning stage, the upscaling can consider temporal variations and achieves improved frame-to-frame coherence. We demonstrate the quality of the network for Isosurfaces which were never seen during training, and discuss remote and in-situ visualization as well as focus+context visualization as potential applications
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visualizing the positional and geometrical variability of Isosurfaces in uncertain scalar fields
IEEE VGTC Conference on Visualization, 2011Co-Authors: Tobias Pfaffelmoser, Matthias Reitinger, Rudiger WestermannAbstract:We present a novel approach for visualizing the positional and geometrical variability of Isosurfaces in uncertain 3D scalar fields. Our approach extends recent work by Pothkow and Hege [PH10] in that it accounts for correlations in the data to determine more reliable isosurface crossing probabilities. We introduce an incremental updatescheme that allows integrating the probability computation into front-to-back volume ray-casting efficiently. Our method accounts for homogeneous and anisotropic correlations, and it determines for each sampling interval along a ray the probability of crossing an isosurface for the first time. To visualize the positional and geometrical uncertainty even under viewing directions parallel to the surface normal, we propose a new color mapping scheme based on the approximate spatial deviation of possible surface points from the mean surface. The additional use of saturation enables to distinguish between areas of high and low statistical dependence. Experimental results confirm the effectiveness of our approach for the visualization of uncertainty related to position and shape of convex and concave isosurface structures.
Stephen M De Bruyn Kops - One of the best experts on this subject based on the ideXlab platform.
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area of scalar Isosurfaces in homogeneous isotropic turbulence as a function of reynolds and schmidt numbers
Journal of Fluid Mechanics, 2020Co-Authors: Kedar Prashant Shete, Stephen M De Bruyn KopsAbstract:A fundamental effect of fluid turbulence is turbulent mixing, which results in the stretching and wrinkling of scalar Isosurfaces. Thus, the area of Isosurfaces is of interest in understanding turbulence in general, with specific applications in, for example, combustion and the identification of turbulent/non-turbulent interfaces. We report measurements of isosurface areas in 28 direct numerical simulations (DNS) of homogeneous isotropic turbulence with a mean scalar gradient resolved on up to grid points with Taylor Reynolds number ranging from 24 to 633 and Schmidt number ranging from 0.1 to 7. More precisely, we measure layers with very small but finite thickness. The continuous equation we evaluate converges exactly to the area in the limit of zero layer thickness. We demonstrate a method for numerically integrating this equation that, for a test case with an analytical solution, converges linearly towards the exact solution with decreasing layer width. By applying the technique to DNS data and testing for convergence with resolution of the simulations, we verify the resolution requirements for DNS recently proposed by Yeung et al. (Phys. Rev. Fluids, vol. 3 (6), 2018, 064603). We conclude that isosurface areas scale with the square root of the Taylor Peclet number between approximately 50 and 4429, with some departure from power-law scaling evident for . No independent effect of either or is observed. The excellent scaling of area with occurs even though the probability density function of the scalar gradient is very close to exponential for but approximately lognormal when .
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area of scalar Isosurfaces in homogeneous isotropic turbulence as a function of reynolds and schmidt numbers
Journal of Fluid Mechanics, 2020Co-Authors: Kedar Prashant Shete, Stephen M De Bruyn KopsAbstract:A fundamental effect of fluid turbulence is turbulent mixing, which results in the stretching and wrinkling of scalar Isosurfaces. Thus, the area of Isosurfaces is of interest in understanding turbulence in general, with specific applications in, for example, combustion and the identification of turbulent/non-turbulent interfaces. We report measurements of isosurface areas in 28 direct numerical simulations (DNS) of homogeneous isotropic turbulence with a mean scalar gradient resolved on up to $14\,256^{3}$ grid points with Taylor Reynolds number $Re_{\unicode[STIX]{x1D706}}$ ranging from 24 to 633 and Schmidt number $Sc$ ranging from 0.1 to 7. More precisely, we measure layers with very small but finite thickness. The continuous equation we evaluate converges exactly to the area in the limit of zero layer thickness. We demonstrate a method for numerically integrating this equation that, for a test case with an analytical solution, converges linearly towards the exact solution with decreasing layer width. By applying the technique to DNS data and testing for convergence with resolution of the simulations, we verify the resolution requirements for DNS recently proposed by Yeung et al. ( Phys. Rev. Fluids , vol. 3 (6), 2018, 064603). We conclude that isosurface areas scale with the square root of the Taylor Peclet number $Pe_{\unicode[STIX]{x1D706}}$ between approximately 50 and 4429, with some departure from power-law scaling evident for $2.4
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area of scalar Isosurfaces in homogeneous isotropic turbulence as a function of reynolds and schmidt numbers
Journal of Fluid Mechanics, 2020Co-Authors: Kedar Prashant Shete, Stephen M De Bruyn KopsAbstract:A fundamental effect of fluid turbulence is turbulent mixing, which results in the stretching and wrinkling of scalar Isosurfaces. Thus, the area of Isosurfaces is of interest in understanding turbulence in general, with specific applications in, for example, combustion and the identification of turbulent/non-turbulent interfaces. We report measurements of isosurface areas in 28 direct numerical simulations (DNS) of homogeneous isotropic turbulence with a mean scalar gradient resolved on up to .
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area of scalar Isosurfaces in homogeneous isotropic turbulence as a function of reynolds and schmidt numbers
arXiv: Fluid Dynamics, 2019Co-Authors: Kedar Prashant Shete, Stephen M De Bruyn KopsAbstract:A fundamental effect of fluid turbulence is turbulent mixing, which results in the stretching and wrinkling of scalar Isosurfaces. Thus, the area of Isosurfaces is of interest in understanding turbulence in general with specific applications in, e.g., combustion and the identification of turbulent/non-turbulent interfaces. We report measurements of isosurface areas in 28 direct numerical simulations (DNSs) of homogeneous isotropic turbulence with a mean scalar gradient resolved on up to $14256^3$ grid points with Taylor Reynolds number $Re{_\lambda}$ ranging from 24 to 633 and Schmidt number $Sc$ ranging from 0.1 to 7. More precisely, we measure layers with very small but finite thickness. The continuous equation we evaluate converges exactly to the area in the limit of zero layer thickness. We demonstrate a method for numerically integrating this equation that, for a test case with an analytical solution, converges linearly towards the exact solution with decreasing layer width. By applying the technique to DNS data and testing for convergence with resolution of the simulations, we verify the resolution requirements for DNS recently proposed by \citet{yeung18}. We conclude that isosurface areas scale with the square root of the Taylor P\'eclet number $Pe_{\lambda}$ between approximately 50 and 4429 with some departure from power law scaling evident for $2.4 < Pe_{\lambda} < 50$. No independent effect of either $Re_{\lambda}$ or $Sc$ is observed. The excellent scaling of area with $Pe_{\lambda}^{1/2}$ occurs even though the probability density function (p.d.f.) of the scalar gradient is very close to exponential for $Re_{\lambda}=98$ but approximately lognormal when $Re_{\lambda}=633$.
Laura J Juszczak - One of the best experts on this subject based on the ideXlab platform.
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the broken ring reduced aromaticity in lys trp cations and high ph tautomer correlates with lower quantum yield and shorter lifetimes
Journal of Physical Chemistry B, 2014Co-Authors: Azaria S Eisenberg, Laura J JuszczakAbstract:Several nonradiative processes compete with tryptophan fluorescence emission. The difficulty in spectral interpretation lies in associating specific molecular environmental features with these processes and thereby utilizing the fluorescence spectral data to identify the local environment of tryptophan. Here, spectroscopic and molecular modeling study of Lys-Trp dipeptide charged species shows that backbone-ring interactions are undistinguished. Instead, quantum mechanical ground state Isosurfaces reveal variations in indole π electron distribution and density that parallel charge (as a function of pK1, pK2, and pKR) on the backbone and residues. A pattern of aromaticity-associated quantum yield and fluorescence lifetime changes emerges. Where quantum yield is high, Isosurfaces have a charge distribution similar to the highest occupied molecular orbital (HOMO) of indole, which is the dominant fluorescent ground state of the 1La transition dipole moment. Where quantum yield is low, isosurface charge distri...
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the broken ring reduced aromaticity in lys trp cations and high ph tautomer correlates with lower quantum yield and shorter lifetimes
The Journal of Physical Chemistry, 2014Co-Authors: Azaria S Eisenberg, Laura J JuszczakAbstract:Several nonradiative processes compete with tryptophan fluorescence emission. The difficulty in spectral interpretation lies in associating specific molecular environmental features with these processes and thereby utilizing the fluorescence spectral data to identify the local environment of tryptophan. Here, spectroscopic and molecular modeling study of Lys-Trp dipeptide charged species shows that backbone-ring interactions are undistinguished. Instead, quantum mechanical ground state Isosurfaces reveal variations in indole π electron distribution and density that parallel charge (as a function of pK₁, pK₂, and pKR) on the backbone and residues. A pattern of aromaticity-associated quantum yield and fluorescence lifetime changes emerges. Where quantum yield is high, Isosurfaces have a charge distribution similar to the highest occupied molecular orbital (HOMO) of indole, which is the dominant fluorescent ground state of the ¹Lₐ transition dipole moment. Where quantum yield is low, isosurface charge distribution over the ring is uneven, diminished, and even found off ring. At pH 13, the indole amine is deprotonated, and Lys-Trp quantum yield is extremely low due to tautomer structure that concentrates charge on the indole amine; the isosurface charge distribution bears scant resemblance to the indole HOMO. Such greatly diminished fluorescence has been observed for proteins where the indole nitrogen is hydrogen bonded, lending credence to the association of aromaticity changes with diminished quantum yield in proteins as well. Thus tryptophan ground state Isosurfaces are an indicator of indole aromaticity, signaling the partition of excitation energy between radiative and nonradiative processes.
Kedar Prashant Shete - One of the best experts on this subject based on the ideXlab platform.
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area of scalar Isosurfaces in homogeneous isotropic turbulence as a function of reynolds and schmidt numbers
Journal of Fluid Mechanics, 2020Co-Authors: Kedar Prashant Shete, Stephen M De Bruyn KopsAbstract:A fundamental effect of fluid turbulence is turbulent mixing, which results in the stretching and wrinkling of scalar Isosurfaces. Thus, the area of Isosurfaces is of interest in understanding turbulence in general, with specific applications in, for example, combustion and the identification of turbulent/non-turbulent interfaces. We report measurements of isosurface areas in 28 direct numerical simulations (DNS) of homogeneous isotropic turbulence with a mean scalar gradient resolved on up to grid points with Taylor Reynolds number ranging from 24 to 633 and Schmidt number ranging from 0.1 to 7. More precisely, we measure layers with very small but finite thickness. The continuous equation we evaluate converges exactly to the area in the limit of zero layer thickness. We demonstrate a method for numerically integrating this equation that, for a test case with an analytical solution, converges linearly towards the exact solution with decreasing layer width. By applying the technique to DNS data and testing for convergence with resolution of the simulations, we verify the resolution requirements for DNS recently proposed by Yeung et al. (Phys. Rev. Fluids, vol. 3 (6), 2018, 064603). We conclude that isosurface areas scale with the square root of the Taylor Peclet number between approximately 50 and 4429, with some departure from power-law scaling evident for . No independent effect of either or is observed. The excellent scaling of area with occurs even though the probability density function of the scalar gradient is very close to exponential for but approximately lognormal when .
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area of scalar Isosurfaces in homogeneous isotropic turbulence as a function of reynolds and schmidt numbers
Journal of Fluid Mechanics, 2020Co-Authors: Kedar Prashant Shete, Stephen M De Bruyn KopsAbstract:A fundamental effect of fluid turbulence is turbulent mixing, which results in the stretching and wrinkling of scalar Isosurfaces. Thus, the area of Isosurfaces is of interest in understanding turbulence in general, with specific applications in, for example, combustion and the identification of turbulent/non-turbulent interfaces. We report measurements of isosurface areas in 28 direct numerical simulations (DNS) of homogeneous isotropic turbulence with a mean scalar gradient resolved on up to $14\,256^{3}$ grid points with Taylor Reynolds number $Re_{\unicode[STIX]{x1D706}}$ ranging from 24 to 633 and Schmidt number $Sc$ ranging from 0.1 to 7. More precisely, we measure layers with very small but finite thickness. The continuous equation we evaluate converges exactly to the area in the limit of zero layer thickness. We demonstrate a method for numerically integrating this equation that, for a test case with an analytical solution, converges linearly towards the exact solution with decreasing layer width. By applying the technique to DNS data and testing for convergence with resolution of the simulations, we verify the resolution requirements for DNS recently proposed by Yeung et al. ( Phys. Rev. Fluids , vol. 3 (6), 2018, 064603). We conclude that isosurface areas scale with the square root of the Taylor Peclet number $Pe_{\unicode[STIX]{x1D706}}$ between approximately 50 and 4429, with some departure from power-law scaling evident for $2.4
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area of scalar Isosurfaces in homogeneous isotropic turbulence as a function of reynolds and schmidt numbers
Journal of Fluid Mechanics, 2020Co-Authors: Kedar Prashant Shete, Stephen M De Bruyn KopsAbstract:A fundamental effect of fluid turbulence is turbulent mixing, which results in the stretching and wrinkling of scalar Isosurfaces. Thus, the area of Isosurfaces is of interest in understanding turbulence in general, with specific applications in, for example, combustion and the identification of turbulent/non-turbulent interfaces. We report measurements of isosurface areas in 28 direct numerical simulations (DNS) of homogeneous isotropic turbulence with a mean scalar gradient resolved on up to .
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area of scalar Isosurfaces in homogeneous isotropic turbulence as a function of reynolds and schmidt numbers
arXiv: Fluid Dynamics, 2019Co-Authors: Kedar Prashant Shete, Stephen M De Bruyn KopsAbstract:A fundamental effect of fluid turbulence is turbulent mixing, which results in the stretching and wrinkling of scalar Isosurfaces. Thus, the area of Isosurfaces is of interest in understanding turbulence in general with specific applications in, e.g., combustion and the identification of turbulent/non-turbulent interfaces. We report measurements of isosurface areas in 28 direct numerical simulations (DNSs) of homogeneous isotropic turbulence with a mean scalar gradient resolved on up to $14256^3$ grid points with Taylor Reynolds number $Re{_\lambda}$ ranging from 24 to 633 and Schmidt number $Sc$ ranging from 0.1 to 7. More precisely, we measure layers with very small but finite thickness. The continuous equation we evaluate converges exactly to the area in the limit of zero layer thickness. We demonstrate a method for numerically integrating this equation that, for a test case with an analytical solution, converges linearly towards the exact solution with decreasing layer width. By applying the technique to DNS data and testing for convergence with resolution of the simulations, we verify the resolution requirements for DNS recently proposed by \citet{yeung18}. We conclude that isosurface areas scale with the square root of the Taylor P\'eclet number $Pe_{\lambda}$ between approximately 50 and 4429 with some departure from power law scaling evident for $2.4 < Pe_{\lambda} < 50$. No independent effect of either $Re_{\lambda}$ or $Sc$ is observed. The excellent scaling of area with $Pe_{\lambda}^{1/2}$ occurs even though the probability density function (p.d.f.) of the scalar gradient is very close to exponential for $Re_{\lambda}=98$ but approximately lognormal when $Re_{\lambda}=633$.