Parzsweep: A Novel Parallel Algorithm for Volume Rendering of Regular Datasets

The sweep paradigm for volume rendering has previously been successfully applied with irregular grids. This thesis describes a parallel volume rendering algorithm called PARZSweep for regular grids that utilizes the sweep paradigm. The sweep paradigm is a concept where a plane sweeps the data volume parallel to the viewing direction. As the sweeping proceeds in the increasing order of z, the faces incident on the vertices are projected onto the viewing volume to constitute to the image. The sweeping ensures that all faces are projected in the correct order and the image thus obtained is very accurate in its details. PARZSweep is an extension of a serial algorithm for regular grids called RZSweep. The hypothesis of this research is that a parallel version of RZSweep can be designed and implemented which will utilize multiple processors to reduce rendering times. PARZSweep follows an approach called image-based task scheduling or tiling. This approach divides the image space into tiles and allocates each tile to a processor for individual rendering. The sub images are composite to form a complete final image. PARZSweep uses a shared memory architecture in order to take advantage of inherent cache coherency for faster communication between processor. Experiments were conducted comparing RZSweep and PARZSweep with respect to prerendering times, rendering times and image quality. RZSweep and PARZSweep have approximately the same prerendering costs, produce exactly the same images and PARZSweep substantially reduced rendering times. PARZSweep was evaluated for scalability with respect to the number of tiles and number of processors. Scalability results were disappointing due to uneven data distribution

Image-space decomposition algorithms for sort-first parallel volume rendering of unstructured grids

Twelve adaptive image-space decomposition algorithms are presented for sort-first parallel direct volume rendering (DVR) of unstructured grids on distributed-memory 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 workload-array 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 screen-space bounding boxes of the primitives in a screen region in constant time. A probe-based chains-on-chains partitioning algorithm is exploited for load balancing in optimal 1D decomposition and iterative 2D rectilinear decomposition (RD). A new probe-based optimal 2D jagged decomposition (OJD) is proposed which is much faster than the dynamic-programming based OJD scheme proposed in the literature. The summed-area table is successfully exploited to query the workload of a rectangular region in constant time in both OJD and RD schemes for the subdivision of general 2D workload arrays. Two orthogonal recursive bisection (ORB) variants are adapted to relax the straight-line division restriction in conventional ORB through using the medians-of-medians approach on regular mesh and quadtree superimposed on the screen. Two approaches based on the Hilbert space-filling curve and graph-partitioning are also proposed. An efficient primitive classification scheme is proposed for redistribution in 1D, and 2D rectilinear and jagged decompositions. The performance comparison of the decomposition algorithms is modeled by establishing appropriate quality measures for load-balancing, amount of primitive replication and parallel execution time. The experimental results on a Parsytec CC system using a set of benchmark volumetric datasets verify the validity of the proposed performance models. The performance evaluation of the decomposition algorithms is also carried out through the sort-first parallelization of an efficient DVR algorithm

Image-space decomposition algorithms for sort-first parallel volume rendering of unstructured grids

Ankara : Department of Computer Engineering and Information Science and the Institute of Engineering and Science of Bilkent University, 1997.Thesis (Master's) -- Bilkent University, 1997.Includes bibliographical references leaves 96-100.Kutluca, HüseyinM.S

Granite: A scientific database model and implementation

The principal goal of this research was to develop a formal comprehensive model for representing highly complex scientific data. An effective model should provide a conceptually uniform way to represent data and it should serve as a framework for the implementation of an efficient and easy-to-use software environment that implements the model. The dissertation work presented here describes such a model and its contributions to the field of scientific databases. In particular, the Granite model encompasses a wide variety of datatypes used across many disciplines of science and engineering today. It is unique in that it defines dataset geometry and topology as separate conceptual components of a scientific dataset. We provide a novel classification of geometries and topologies that has important practical implications for a scientific database implementation. The Granite model also offers integrated support for multiresolution and adaptive resolution data. Many of these ideas have been addressed by others, but no one has tried to bring them all together in a single comprehensive model. The datasource portion of the Granite model offers several further contributions. In addition to providing a convenient conceptual view of rectilinear data, it also supports multisource data. Data can be taken from various sources and combined into a unified view. The rod storage model is an abstraction for file storage that has proven an effective platform upon which to develop efficient access to storage. Our spatial prefetching technique is built upon the rod storage model, and demonstrates very significant improvement in access to scientific datasets, and also allows machines to access data that is far too large to fit in main memory. These improvements bring the extremely large datasets now being generated in many scientific fields into the realm of tractability for the ordinary researcher. We validated the feasibility and viability of the model by implementing a significant portion of it in the Granite system. Extensive performance evaluations of the implementation indicate that the features of the model can be provided in a user-friendly manner with an efficiency that is competitive with more ad hoc systems and more specialized application specific solutions

High performance computer simulated bronchoscopy with interactive navigation.

by Ping-Fu Fung.Thesis (M.Phil.)--Chinese University of Hong Kong, 1998.Includes bibliographical references (leaves 98-102).Abstract also in Chinese.Abstract --- p.ivAcknowledgements --- p.viChapter 1 --- Introduction --- p.1Chapter 1.1 --- Medical Visualization System --- p.4Chapter 1.1.1 --- Data Acquisition --- p.4Chapter 1.1.2 --- Computer-aided Medical Visualization --- p.5Chapter 1.1.3 --- Existing Systems --- p.6Chapter 1.2 --- Research Goal --- p.8Chapter 1.2.1 --- System Architecture --- p.9Chapter 1.3 --- Organization of this Thesis --- p.10Chapter 2 --- Volume Visualization --- p.11Chapter 2.1 --- Sampling Grid and Volume Representation --- p.11Chapter 2.2 --- Priori Work in Volume Rendering --- p.13Chapter 2.2.1 --- Surface VS Direct --- p.14Chapter 2.2.2 --- Image-order VS Object-order --- p.18Chapter 2.2.3 --- Orthogonal VS Perspective --- p.22Chapter 2.2.4 --- Hardware Acceleration VS Software Acceleration --- p.23Chapter 2.3 --- Chapter Summary --- p.29Chapter 3 --- IsoRegion Leaping Technique for Perspective Volume Rendering --- p.30Chapter 3.1 --- Compositing Projection in Direct Volume Rendering --- p.31Chapter 3.2 --- IsoRegion Leaping Acceleration --- p.34Chapter 3.2.1 --- IsoRegion Definition --- p.35Chapter 3.2.2 --- IsoRegion Construction --- p.37Chapter 3.2.3 --- IsoRegion Step Table --- p.38Chapter 3.2.4 --- Ray Traversal Scheme --- p.41Chapter 3.3 --- Experiment Result --- p.43Chapter 3.4 --- Improvement --- p.47Chapter 3.5 --- Chapter Summary --- p.48Chapter 4 --- Parallel Volume Rendering by Distributed Processing --- p.50Chapter 4.1 --- Multi-platform Loosely-coupled Parallel Environment Shell --- p.51Chapter 4.2 --- Distributed Rendering Pipeline (DRP) --- p.55Chapter 4.2.1 --- Network Architecture of a Loosely-Coupled System --- p.55Chapter 4.2.2 --- Data and Task Partitioning --- p.58Chapter 4.2.3 --- Communication Pattern and Analysis --- p.59Chapter 4.3 --- Load Balancing --- p.69Chapter 4.4 --- Heterogeneous Rendering --- p.72Chapter 4.5 --- Chapter Summary --- p.73Chapter 5 --- User Interface --- p.74Chapter 5.1 --- System Design --- p.75Chapter 5.2 --- 3D Pen Input Device --- p.76Chapter 5.3 --- Visualization Environment Integration --- p.77Chapter 5.4 --- User Interaction: Interactive Navigation --- p.78Chapter 5.4.1 --- Camera Model --- p.79Chapter 5.4.2 --- Zooming --- p.81Chapter 5.4.3 --- Image View --- p.82Chapter 5.4.4 --- User Control --- p.83Chapter 5.5 --- Chapter Summary --- p.87Chapter 6 --- Conclusion --- p.88Chapter 6.1 --- Final Summary --- p.88Chapter 6.2 --- Deficiency and Improvement --- p.89Chapter 6.3 --- Future Research Aspect --- p.91Appendix --- p.93Chapter A --- Common Error in Pre-multiplying Color and Opacity --- p.94Chapter B --- Binary Factorization of the Sample Composition Equation --- p.9

MiniAMR - A miniapp for Adaptive Mesh Refinement

This report describes the detailed implementation of MiniAMR - a software for octree-based adaptive mesh refinement (AMR) that can be used to study the communication costs in a typical AMR simulation. We have designed new data structures and refinement/coarsening algorithms for octree-based AMR and studied the performance improvements using a similar software from Sandia National Laboratory. We have also introduced the idea of amortized load balancing to AMR in this report. In addition to this, we have also provided a low-overhead distributed load balancing scheme for AMR applications that perform sub-cycling (refinement in time).Ope

Exploiting replicated data for communication load balancing in image-space parallel direct volume rendering of unstructured grids

Ankara : The Department of Computer Engineering and Information Science and the Institute of Engineering and Science of Bilkent Univ., 2009.Thesis (Master's) -- Bilkent University, 2009.Includes bibliographical references leaves 89-94.The focus of this work is on parallel volume rendering applications in which renderings with different parameters are successively repeated over the same dataset. The only reason for inter-task interaction is the existence of data primitives that are inputs to several tasks. Both computational structure and expected task execution times may change during successive rendering instances. Change in computational structure means change in the data primitive requirements of tasks. Since the individual processors of a parallel system have a limited storage capacity, we can reserve a limited amount of storage for holding replicas at each processor. For the parallelization of a particular rendering instance, the remapping model should utilize the replication pattern of the previous rendering instance(s) for reducing the communication overhead due to the data replication requirement of the current rendering instance. We propose a two-phase model for solving this problem. The hypergraphpartitioning-based model proposed for the first phase aims to minimize the total message volume that will be incurred due to the replication/migration of input data while maintaining balance on computational and receive-volume loads of processors. The network-flow-based model proposed for the second phase aims to minimize the maximum message volume handled by processors via utilizing the flexibility in assigning send-communication tasks to processors, which is introduced by data replication. The validity of our proposed model is verified on image-space parallelization of a direct volume rendering algorithm.Okuyan, ErkanM.S

Lattice-Boltzmann simulations of cerebral blood flow

Computational haemodynamics play a central role in the understanding of blood behaviour in the cerebral vasculature, increasing our knowledge in the onset of vascular diseases and their progression, improving diagnosis and ultimately providing better patient prognosis. Computer simulations hold the potential of accurately characterising motion of blood and its interaction with the vessel wall, providing the capability to assess surgical treatments with no danger to the patient. These aspects considerably contribute to better understand of blood circulation processes as well as to augment pre-treatment planning. Existing software environments for treatment planning consist of several stages, each requiring significant user interaction and processing time, significantly limiting their use in clinical scenarios. The aim of this PhD is to provide clinicians and researchers with a tool to aid in the understanding of human cerebral haemodynamics. This tool employs a high performance fluid solver based on the lattice-Boltzmann method (coined HemeLB), high performance distributed computing and grid computing, and various advanced software applications useful to efficiently set up and run patient-specific simulations. A graphical tool is used to segment the vasculature from patient-specific CT or MR data and configure boundary conditions with ease, creating models of the vasculature in real time. Blood flow visualisation is done in real time using in situ rendering techniques implemented within the parallel fluid solver and aided by steering capabilities; these programming strategies allows the clinician to interactively display the simulation results on a local workstation. A separate software application is used to numerically compare simulation results carried out at different spatial resolutions, providing a strategy to approach numerical validation. This developed software and supporting computational infrastructure was used to study various patient-specific intracranial aneurysms with the collaborating interventionalists at the National Hospital for Neurology and Neuroscience (London), using three-dimensional rotational angiography data to define the patient-specific vasculature. Blood flow motion was depicted in detail by the visualisation capabilities, clearly showing vortex fluid ow features and stress distribution at the inner surface of the aneurysms and their surrounding vasculature. These investigations permitted the clinicians to rapidly assess the risk associated with the growth and rupture of each aneurysm. The ultimate goal of this work is to aid clinical practice with an efficient easy-to-use toolkit for real-time decision support