141 research outputs found
A Multi-Resolution Interactive Previewer for Volumetric Data on Arbitary Meshes
In this paper we describe a rendering method suitable for interactive previewing of large-scale arbitary-mesh volume data sets. A data set to be visualized is represented by a ''point cloud,'' i. e., a set of points and associated data values without known connectivity between the points. The method uses a multi-resolution approach to achieve interactive rendering rates of several frames per second for arbitrarily large data sets. Lower-resolution approximations of an original data set are created by iteratively applying a point- decimation operation to higher-resolution levels. The goal of this method is to provide the user with an interactive navigation and exploration tool to determine good viewpoints and transfer functions to pass on to a high-quality volume renderer that uses a standard algorithm
Dynamic view-dependent visualization of unstructured tetrahedral volumetric meshes
Visualization of large volumetric datasets has always been an important problem. Due to the high computational requirements of volume-rendering techniques, achieving interactive rates is a real challenge. We present a selective refinement scheme that dynamically refines the mesh according to the camera parameters. This scheme automatically determines the impact of different parts of the mesh on the output image and refines the mesh accordingly, without needing any user input. The view-dependent refinement scheme uses a progressive mesh representation that is based on an edge collapse-based tetrahedral mesh simplification algorithm. We tested our view-dependent refinement framework on an existing state-of-theart volume renderer. Thanks to low overhead dynamic view-dependent refinement, we achieve interactive frame rates for rendering common datasets at decent image resolutions. © 2012 The Visualization Society of Japan
Patient specific numerical simulation of flow in the human upper airways for assessing the effect of nasal surgery
The study is looking into the potential of using computational fluid dynamics
(CFD) as a tool for predicting the outcome of surgery for alleviation of
obstructive sleep apnea syndrome (OSAS). From pre- and post-operative computed
tomography (CT) of an OSAS patient, the pre- and post-operative geometries of
the patient's upper airways were generated. CFD simulations of laminar flow in
the patient's upper airway show that after nasal surgery the mass flow is more
evenly distributed between the two nasal cavities and the pressure drop over
the nasal cavity has increased. The pressure change is contrary to clinical
measurements that the CFD results have been compared with, and this is most
likely related to the earlier steps of modelling - CT acquisition and geometry
retrieval.Comment: Proceedings of the 12th International Conference on CFD in Oil & Gas,
Metallurgical and Process Industries, Trondheim, Norway, May 30th - June 1st,
2017, 11 pages, 13 figure
Optimum Slice Reduction Algorithm For Fast Surface Reconstruction From Contour Slices
Tesis ini memfokus kepada pembinaan semula permukaan daripada siri hirisan
kontur, dengan tujuan mempercepatkan proses pembinaan semula di samping
mengekalkan kualiti output pada tahap yang boleh diterima.
This thesis is concerned with the reconstruction of surface from a series of
contour slices, with the aim to speed up the reconstruction process while preserving
the output quality at an acceptable level
Optimum Slice Reduction Algorithm For Fast Surface Reconstruction From Contour slices [QA571. T164 2007 f rb].
Tesis ini memfokus kepada pembinaan semula permukaan daripada siri hirisan kontur, dengan tujuan mempercepatkan proses pembinaan semula di samping mengekalkan kualiti output pada tahap yang boleh diterima. Teknik yang dicadangkan dalam tesis ini memproses hirisan-hirisan kontur sebelum pembinaan semula permukaan.
This thesis is concerned with the reconstruction of surface from a series of contour slices, with the aim to speed up the reconstruction process while preserving the output quality at an acceptable level. The proposed technique in this thesis, preprocesses the slices of contour prior to surface reconstruction
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Hierarchical Large-scale Volume Representation with 3rd-root-of-2 Subdivision and Trivariate B-spline Wavelets
Multiresolution methods provide a means for representing data at multiple levels of detail. They are typically based on a hierarchical data organization scheme and update rules needed for data value computation. We use a data organization that is based on what we call subdivision. The main advantage of subdivision, compared to quadtree (n=2) or octree (n=3) organizations, is that the number of vertices is only doubled in each subdivision step instead of multiplied by a factor of four or eight, respectively. To update data values we use n-variate B-spline wavelets, which yield better approximations for each level of detail. We develop a lifting scheme for n=2 and n=3 based on the -subdivision scheme. We obtain narrow masks that provide a basis for out-of-core techniques as well as view-dependent visualization and adaptive, localized refinement
Volumetric rendering techniques for scientific visualization
Ankara : The Department of Computer Engineering and The Graduate School of Engineering and Science of Bilkent University, 2014.Thesis (Ph.D.) -- Bilkent University, 2014.Includes bibliographical references leaves 80-86.Direct volume rendering is widely used in many applications where the inside of a
transparent or a partially transparent material should be visualized. We have explored
several aspects of the problem. First, we proposed a view-dependent selective refinement
scheme in order to reduce the high computational requirements without affecting
the image quality significantly. Then, we explored the parallel implementations of
direct volume rendering: both on GPU and on multi-core systems. Finally, we used direct
volume rendering approaches to create a tool, MaterialVis, to visualize amorphous
and/or crystalline materials.
Visualization of large volumetric datasets has always been an important problem.
Due to the high computational requirements of volume-rendering techniques, achieving
interactive rates is a real challenge. We present a selective refinement scheme
that dynamically refines the mesh according to the camera parameters. This scheme
automatically determines the impact of different parts of the mesh on the output image
and refines the mesh accordingly, without needing any user input. The viewdependent
refinement scheme uses a progressive mesh representation that is based
on an edge collapse-based tetrahedral mesh simplification algorithm. We tested our
view-dependent refinement framework on an existing state-of-the-art volume renderer.
Thanks to low overhead dynamic view-dependent refinement, we achieve interactive
frame rates for rendering common datasets at decent image resolutions.
Achieving interactive rates for direct volume rendering of large unstructured volumetric
grids is a challenging problem, but parallelizing direct volume rendering algorithms
can help achieve this goal. Using Compute Unified Device Architecture
(CUDA), we propose a GPU-based volume rendering algorithm that itself is based on
a cell projection-based ray-casting algorithm designed for CPU implementations. We
also propose a multi-core parallelized version of the cell-projection algorithm using OpenMP. In both algorithms, we favor image quality over rendering speed. Our algorithm
has a low memory footprint, allowing us to render large datasets. Our algorithm
support progressive rendering. We compared the GPU implementation with the serial
and multi-core implementations. We observed significant speed-ups, that, together
with progressive rendering, enabling reaching interactive rates for large datasets.
Visualization of materials is an indispensable part of their structural analysis. We
developed a visualization tool for amorphous as well as crystalline structures, called
MaterialVis. Unlike the existing tools, MaterialVis represents material structures as a
volume and a surface manifold, in addition to plain atomic coordinates. Both amorphous
and crystalline structures exhibit topological features as well as various defects.
MaterialVis provides a wide range of functionality to visualize such topological structures
and crystal defects interactively. Direct volume rendering techniques are used
to visualize the volumetric features of materials, such as crystal defects, which are
responsible for the distinct fingerprints of a specific sample. In addition, the tool provides
surface visualization to extract hidden topological features within the material.
Together with the rich set of parameters and options to control the visualization, MaterialVis
allows users to visualize various aspects of materials very efficiently as generated
by modern analytical techniques such as the Atom Probe Tomography.Okuyan, ErhanPh.D
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