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Computer Graphics and Applications, IEEE

Issue 4 • Date July 1994

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Displaying Results 1 - 10 of 10
  • The cosmic worm

    Page(s): 12 - 14
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (238 KB)  

    Sometimes scientists would like to put their heads into interesting parts of their data sets and look around, but they are hampered by the "outside looking in" aspect of workstation-based visualization. At the Electronic Visualization Laboratory (EVL) at the University of Illinois at Chicago, we are attempting to break some of the visualization barriers with a distributed computing and visualization environment developed using the Cave Automatic Virtual Environment (CAVE) virtual reality theater. In particular, we are trying to provide physicists and astrophysicists at the National Center for Supercomputing Applications (NCSA) a new vehicle for scientific discovery.<> View full abstract»

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  • Decriminalizing the fingerprint

    Page(s): 15 - 16
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (238 KB)  

    This is the first in a two-part series on computer graphics in identification. This installment looks at the increasing popularity of automated fingerprint identification systems. The second article will consider other methods on the rise, including facial recognition systems.<> View full abstract»

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  • Bump shading for volume textures

    Page(s): 18 - 20
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (254 KB)  

    Bump mapping was introduced as a method of rendering realistic shading on bumpy surfaces, without actually rendering a full 3D model of the bumps. Bump mapping works well for parameterized surfaces. The authors interpret the 3D texture as a displacement function to be added to the surface position.<> View full abstract»

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  • A sorting classification of parallel rendering

    Page(s): 23 - 32
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1149 KB)  

    We describe a classification scheme that we believe provides a more structured framework for reasoning about parallel rendering. The scheme is based on where the sort from object coordinates to screen coordinates occurs, which we believe is fundamental whenever both geometry processing and rasterization are performed in parallel. This classification scheme supports the analysis of computational and communication costs, and encompasses the bulk of current and proposed highly parallel renderers - both hardware and software. We begin by reviewing the standard feed-forward rendering pipeline, showing how different ways of parallelizing it lead to three classes of rendering algorithms. Next, we consider each of these classes in detail, analyzing their aggregate processing and communication costs, possible variations, and constraints they may impose on rendering applications. Finally, we use these analyses to compare the classes and identify when each is likely to be preferable.<> View full abstract»

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  • A new algorithm for interactive graphics on multicomputers

    Page(s): 33 - 40
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (786 KB)  

    As nonshared-memory multiple instruction, multiple data (MIMD) systems become more common, it becomes important to develop parallel rendering algorithms for them. These systems, known as multicomputers, can produce data sets so large that it is difficult to visualize the data on conventional graphics systems, especially if the visualization proceeds in tandem with the calculation. Parallel systems must run interactive graphics to allow convenient visualizations of their computations. While few parallel systems currently have a frame buffer that will support interactive rendering, such systems should be more common in the future. This article describes an algorithm suited for interactive polygon rendering, where the model's image on screen generally has frame-to-frame coherence. The algorithm uses this coherence to perform load-balancing calculations in parallel with the other calculations. The algorithm also uses an optimized version of personalized all-to-all communication, where all processors communicate with all other processors.<> View full abstract»

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  • Dynamic load balancing for parallel polygon rendering

    Page(s): 41 - 48
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (770 KB)  

    Using parallel processing for visualization speeds up computer graphics rendering of complex data sets. A parallel algorithm designed for polygon scan conversion and rendering is presented which supports fast rendering of highly complex data sets using advanced lighting models. Dedicated graphics rendering engines do not necessarily suit such data sets, although they can support real-time update of moderately complex scenes using simple lighting. Advantages to using a software-based approach include the feasibility of adding special rendering features to the program and the capability of integrating a parallel scientific application with a parallel graphics renderer. A new work decomposition strategy presented, called task adaptive, is based on dynamically partitioning the amount of computational work left at a given time. The algorithm uses a heuristic for dynamic task decomposition in which image space tasks are partitioned without requiring interruption of the partitioned processor. A sophisticated memory referencing strategy lets local memory access graphics data during rendering. This permits implementation of the algorithm on a distributed memory multiprocessor. An in-depth analysis of the overhead costs accompanying parallel processing shows where performance is adequate or could be improved.<> View full abstract»

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  • Communication costs for parallel volume-rendering algorithms

    Page(s): 49 - 58
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    The computational expense of volume rendering motivates the development of parallel implementations on multicomputers. Parallelism achieves higher frame rates, which provide more natural viewing control and enhanced comprehension of 3D structure. Although many parallel implementations exist, we have no framework to compare their relative merits independent of host hardware. The article attempts to establish that framework by enumerating and classifying parallel volume-rendering algorithms suitable for multicomputers with distributed memory and a communication network. It determined the communication costs for classes of parallel algorithms by considering their inherent communication requirements.<> View full abstract»

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  • Parallel volume rendering using binary-swap compositing

    Page(s): 59 - 68
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1037 KB)  

    We describe a parallel volume-rendering algorithm, which consists of two parts: parallel ray tracing and parallel compositing. In the most recent implementation on Connection Machine's CM-5 and networked workstations, the parallel volume renderer evenly distributes data to the computing resources available. Without the need to communicate with other processing units, each subvolume is ray traced locally and generates a partial image. The parallel compositing process then merges all resulting partial images in depth order to produce the complete image. The compositing algorithm is particularly effective for massively parallel processing, as it always uses all processing units by repeatedly subdividing the partial images and distributing them to the appropriate processing units. Test results on both the CM-5 and the workstations are promising. They do, however, expose different performance issues for each platform.<> View full abstract»

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  • Distributing data and control for ray tracing in parallel

    Page(s): 69 - 77
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    We first briefly describe the methodology of programming ray-tracing algorithms on distributed-memory parallel computers, or DMPCs, and review previous efforts to overcome the problems of data distribution and load balancing. Then we present two algorithms designed for DMPCs and implemented on an Intel iPSC/2. We also compare the results of our experiments with them. The first algorithm, a data-oriented parallel implementation based on message passing, demonstrates how complex designing a parallel ray-tracing algorithm can be. The second algorithm shows how we can eliminate some complexity using a control-oriented parallel approach and a shared virtual memory.<> View full abstract»

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  • Quantization error and dithering

    Page(s): 78 - 82
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (397 KB)  

    Digital storage and transmission promise noise-free images, but it is important to keep in mind that even digital is not perfect. Digital images have their own sources of noise: round-off error and quantization error. Whenever you do any sort of image arithmetic, such as contrast enhancement or compositing, you get roundoff error. In fact, since the arithmetic is often done in only X-bit accuracy, sometimes the round-off error can be substantial. You get quantization error, on the other hand, whenever you go from an analog signal to a digital signal or whenever you go from a high color-resolution signal (for example, 24 bits per pixel) to a low resolution signal (for example, 8 bits per pixel). The author considers the quantization error from analog to digital.<> View full abstract»

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IEEE Computer Graphics and Applications bridges the theory and practice of computer graphics.

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Editor-in-Chief
L. Miguel Encarnação
University of Iowa