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16
A Volume Density Optical Model
, 1992
"... A simple, but accurate, formal volume density optical model is developed for volume rendering scattered data or scalar fields from the finite element method, as opposed to scanned data sets where material classification is involved. The model is suitable either for ray tracing or projection methods ..."
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Cited by 47 (10 self)
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A simple, but accurate, formal volume density optical model is developed for volume rendering scattered data or scalar fields from the finite element method, as opposed to scanned data sets where material classification is involved. The model is suitable either for ray tracing or projection methods and allows maximum flexibility in setting color and opacity. An expression is derived for the light intensity along a ray in terms of six userspecified transfer functions, three for optical density and three for color. Closed form solutions under several different assumptions are presented including a new exact result for the case that the transfer functions vary piecewise linearly along a ray segment within a cell. 1 Introduction An exact simulation of light interacting with a volume density or cloud is quite complex and requires the use of Radiative Transport Theory [2, 6]. However, for the purpose of scientific visualization, less complex simulations can be satisfactory. One of the first...
Particle Tracing Algorithms for 3D Curvilinear Grids
, 1994
"... This chapter presents a comparison of several particle tracing algorithms on curvilinear grids. The fundamentals of particle tracing algorithms are described and used to split tracing algorithms into basic components. Based on this decomposition, two different strategies for particle tracing are de ..."
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Cited by 23 (5 self)
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This chapter presents a comparison of several particle tracing algorithms on curvilinear grids. The fundamentals of particle tracing algorithms are described and used to split tracing algorithms into basic components. Based on this decomposition, two different strategies for particle tracing are described in greater detail: tracing in computational space and tracing in physical space. Accuracy and speed tests are performed for both types of algorithms. From these tests it is concluded that particle tracing algorithms in physical space generally perform better than algorithms in computational space.
On the Optimization of Projective Volume Rendering
, 1995
"... How to render very complex datasets, and yet maintain interactive response times, is a hot topic in volume rendering. In this paper we focus on projective visualization of datasets represented via tetrahedral tessellations. Direct projective visualization is performed by sorting tetrahedra with resp ..."
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Cited by 19 (3 self)
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How to render very complex datasets, and yet maintain interactive response times, is a hot topic in volume rendering. In this paper we focus on projective visualization of datasets represented via tetrahedral tessellations. Direct projective visualization is performed by sorting tetrahedra with respect to view direction and then by projecting them onto the screen. Different sorting algorithms and "per tetrahedra" projection techniques are reviewed and evaluated. A new method for tetrahedra projection approximation is presented. In addition, we compare the results obtained by the optimization of the rendering process with those obtained by adopting a data simplification approach. 1 Introduction The real usability of a system for the visualization of volume data is strictly connected to the level of interactivity the system performs. This is both to simplify the usersystem interaction and to improve our understanding of the results through motion or animation. The efficiency of the vi...
ImageSpace Decomposition Algorithms for SortFirst Parallel Volume Rendering of Unstructured Grids
 The Journal of Supercomputing
, 1997
"... Twelve adaptive imagespace decomposition algorithms are presented for sortfirst parallel direct volume rendering (DVR) of unstructured grids on distributedmemory architectures. The algorithms are presented under a novel taxonomy based on the dimension of the screen decomposition, the dimension of ..."
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Cited by 15 (6 self)
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Twelve adaptive imagespace decomposition algorithms are presented for sortfirst parallel direct volume rendering (DVR) of unstructured grids on distributedmemory architectures. The algorithms are presented under a novel taxonomy based on the dimension of the screen decomposition, the dimension of the workload arrays used in the decomposition, and the scheme used for workloadarray creation and querying the workload of a region. For the 2D decomposition schemes using 2D workload arrays, a novel scheme is proposed to query the exact number of screenspace bounding boxes of the primitives in a screen region in constant time. A probebased chainsonchains partitioning algorithm is exploited for load balancing in optimal 1D decomposition and iterative 2D rectilinear decomposition (RD). A new probebased optimal 2D jagged decomposition (OJD) is proposed which is much faster than the dynamicprogrammingbased OJD scheme proposed in the literature. The summedarea table is successfully explo...
An Architecture for Interactive Tetrahedral Volume Rendering
 In Proc. IEEE/EG Workshop on Volume Graphics ’01
, 2001
"... Abstract. We present a new architecture for interactive unstructured volume rendering. Our system moves all the computations necessary for orderindependent transparency and volume scan conversion from the CPU to the graphics hardware, and it makes a software sorting pass unnecessary. It therefore p ..."
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Cited by 15 (0 self)
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Abstract. We present a new architecture for interactive unstructured volume rendering. Our system moves all the computations necessary for orderindependent transparency and volume scan conversion from the CPU to the graphics hardware, and it makes a software sorting pass unnecessary. It therefore provides the same advantages for volume data that triangleprocessing hardware provides for surfaces. To address a remaining bottleneck – the bandwidth between main memory and the graphics processor – we introduce two new primitives, tetrahedral strips and tetrahedral fans. These primitives allow performance improvements in rendering tetrahedral meshes similar to the improvements triangle strips and fans allow in rendering triangle meshes. We provide new techniques for generating tetrahedral strips that achieve, on the average, strip lengths of 17 on representative datasets. The combined effect of our architecture and new primitives is a 72 to 85 times increase in performance over triangle graphics hardware approaches. These improvements make it possible to use volumetric tetrahedral meshes in interactive applications. 1
Tetrahedra Based Volume Visualization
, 1998
"... . Volume Visualization techniques have advanced considerably since the first international symposium held on this topic eight years ago. This paper briefly reviews the techniques proposed for the visualization of irregular (or scattered) volume datasets. In particular, methods which adopt simplicial ..."
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Cited by 14 (1 self)
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. Volume Visualization techniques have advanced considerably since the first international symposium held on this topic eight years ago. This paper briefly reviews the techniques proposed for the visualization of irregular (or scattered) volume datasets. In particular, methods which adopt simplicial decompositions of E 3 space are considered, and this choice is justified both in terms of modeling and visualization. Simplicial complexes are powerful and robust geometric structures, and a number of efficient visualization algorithms have been proposed. We show that simplicial cells (or simply tetrahedral cells since our target is 3D space) may be conceived as being the unifying kernel primitive for the visualization of notregular meshes. 1 Introduction A volume dataset consists of points in E 3 space, with one or more scalar or vector sample values associated with each point. The need for a visual representation of the content of such datasets led to a substantial research effort a...
HypergraphPartitioningBased Remapping Models for ImageSpaceParallel Direct Volume Rendering of Unstructured Grids
 IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS
, 2005
"... In this work, imagespaceparallel direct volume rendering (DVR) of unstructured grids is investigated for distributedmemory architectures. A hypergraphpartitioningbased model is proposed for the adaptive screen partitioning problem in this context. The proposed model aims to balance the renderin ..."
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Cited by 13 (5 self)
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In this work, imagespaceparallel direct volume rendering (DVR) of unstructured grids is investigated for distributedmemory architectures. A hypergraphpartitioningbased model is proposed for the adaptive screen partitioning problem in this context. The proposed model aims to balance the rendering loads of processors while trying to minimize the amount of data replication. In the parallel DVR framework we adopted, each data primitive is statically owned by its home processor, which is responsible from replicating its primitives on other processors. Two appropriate remapping models are proposed by enhancing the above model for use within this framework. These two remapping models aim to minimize the total volume of communication in data replication while balancing the rendering loads of processors. Based on the proposed models, a parallel DVR algorithm is developed. The experiments conducted on a PC cluster show that the proposed remapping models achieve better speedup values compared to the remapping models previously suggested for imagespaceparallel DVR.
Power Diagram Depth Sorting
 In 10th Canadian Conference on Computational Geometry
, 1998
"... In this paper we propose a new approach to the depth sorting problem. Given a simplicial complex \Gamma in IE d , our approach is based on the preliminary construction of a convex complex \Gamma in IE d+1 , whose projection on IE d corresponds to \Gamma, and on the representation of \Gamma ..."
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Cited by 4 (0 self)
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In this paper we propose a new approach to the depth sorting problem. Given a simplicial complex \Gamma in IE d , our approach is based on the preliminary construction of a convex complex \Gamma in IE d+1 , whose projection on IE d corresponds to \Gamma, and on the representation of \Gamma as a power diagram. This approach exhibits a O(m log m) runtime complexity to sort a simplicial complex with m cells and requires only linear storage. 1 Introduction The problem of sorting a set of objects in space according to their distance from a given viewpoint has been extensively studied in the literature mainly for its important applications in computer graphics. We were interested in this problem because its relevance in volume visualization; another area where the twodimensional version of this problem arises is visibility computation on terrains [8]. Many techniques exist [3] for the direct visualization of an unstructured volumetric dataset orgainized as a tetrahaedral comple...
Direct Volume Rendering of Unstructured Grids
 Computer & Graphics
, 2003
"... This paper investigates three categories of algorithms for direct volume rendering of unstructured grids, which are imagespace, objectspace, and hybrid methods. We propose three new algorithms. Cell Projection (CP) algorithm, which falls into objectspace category, is capable of rendering nonconv ..."
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Cited by 3 (1 self)
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This paper investigates three categories of algorithms for direct volume rendering of unstructured grids, which are imagespace, objectspace, and hybrid methods. We propose three new algorithms. Cell Projection (CP) algorithm, which falls into objectspace category, is capable of rendering nonconvex meshes through a simple yet efficient sorting schema that exploits both image and object space coherencies. Existing hybrid methods use objectthenimage traversal order that enforces the processing of each cell. Thus, these algorithms perform redundant operations and do not support early ray termination. We propose a hybrid method, called SpanBuffer Ray Casting (SBRC), that can support early ray termination discarding redundant operations by employing imagethenobject traversal order. Another hybrid method, called KoyamadaSBRC (KSBRC), is proposed with the motivation of refining imagespace and hybrid methods to extract the best features of them. This method is developed by blending SBRC approach with Koyamada's algorithm, which is an efficient imagespace algorithm. All proposed algorithms are capable of handling acyclic nonconvex meshes and generating images of acceptable quality.