Multi-projector systems are increasingly being used to provide large-scale and high-resolution displays for next-generation interactive 3D graphics applications, including large-scale data visualization, immersive virtual environments, and collaborative design. These systems must include a very high-performance and scalable 3D rendering subsystem in order to generate high-resolution images at real time frame rates. This paper describes a sort-first based parallel rendering system for a scalable display wall system built with a network of PCs, graphics accelerators, and portable projectors. The main challenge is to develop scalable algorithms to partition and assign rendering tasks effectively under the performance and functionality constrains of system area networks, PCs, and commodity 3-D graphics accelerators. We have developed three coarse-grained partitioning algorithms and incorporated them into a working prototype system. This paper describes these algorithms and reports our init...

We investigate a new hybrid of sort-first and sort-last approach for parallel polygon rendering, using as a target platform a cluster of PCs. Unlike previous methods that statically partition the 3D model and/or the 2D image, our approach performs dynamic, viewdependent and coordinated partitioning of both the 3D model and the 2D image. Using a specific algorithm that follows this approach, we show that it performs better than previous approaches and scales better with both processor count and screen resolution. Overall, our algorithm is able to achieve interactive frame rates with efficiencies of 55.0% to 70.5% during simulations of a system with 64 PCs. While it does have potential disadvantages in client-side processing and in dynamic data management---which also stem from its dynamic, view-dependent nature---these problems are likely to diminish with technology trends in the future. Keywords: Parallel rendering, cluster computing. 1 Introduction The objective of our research is ...

In computer graphics, rendering is the process by which an abstract description of a scene is converted to an image. When the scene is complex, or when high-quality images or high frame rates are required, the rendering process becomes computationally demanding. To provide the necessary levels of performance, parallel computing techniques must be brought to bear. Although parallelism has been exploited in computer graphics since the early days of the field, its initial use was primarily in specialized applications. The VLSI revolution of the late 1970Õs and the advent of scalable parallel computers during the late 1980Õs changed this situation. Today, parallel hardware is routinely used in graphics workstations, and numerous software-based rendering systems have been developed for general-purpose parallel architectures. This article provides a broad introduction to the subject of parallel rendering, encompassing both hardware and software systems. The focus is on the underlying concepts and the issues which arise in the design of parallel rendering algorithms and systems. We examine the different types of parallelism and how they can be applied in rendering applications. Concepts from parallel computing, such as data decomposition, task granularity, scalability, and load balancing, are considered in relation to the rendering

In this paper, a case study is presented which is aimed at investigating the performance of several parallel versions of the POV--Ray raytracing package implemented on a workstation cluster using the MPI message passing library. Based on a manager/worker scheme, variants of workload partitioning and message scheduling strategies, in conjunction with different task granularities, are evaluated with respect to their runtime behaviour. The results indicate that dynamic, adaptive strategies are required to cope with both the unbalanced workload characteristics of the parallel raytracing application and the different computational capabilities of the machines in a workstation cluster environment. 1 Introduction Raytracing [9, 13, 24] is a widely used method for generating realistically looking images on a computer, and it is employed by many 3D modelling and animation systems for the final image rendering. The input to a raytracing algorithm is the scene -- the description of the geometry...

This dissertation identifies a class of parallel polygon rendering algorithms suitable for interactive use on multicomputers, and presents a methodology for designing efficient algorithms within that class. The methodology was used to design a new polygon rendering algorithm that uses the frame-to-frame coherence of the screen image to evenly partition the rasterization at reasonable cost. An implementation of the algorithm on the Intel Touchstone Delta at Caltech, the largest multicomputer at the time, renders 3.1 million triangles per second. The rate was measured using a 806,640 triangle model and 512 i860 processors, and includes back-facing triangles. A similar algorithm is used in Pixel-Planes 5, a system that has specialized rasterization processors, and which, when introduced, had a benchmark score for the SPEC Graphics Performance Characterization Group "head" benchmark that was nearly four times faster than commercial workstations. The algorithm design methodology also ident...

This paper describes the implementation and performance evaluation of a 3D graphics library that can be readily linked with parallel applications to provide run-time visualization on large-scale message-passing parallel machines, such as Intel Paragon. The prototype implementation is currently fully operational, and is based on a public-domain OpenGL implementation Mesa, and a sort-last parallelization strategy. Through a detailed performance analysis, we show that the scalability of the current prototype is close to the theoretical limit for the given hardware architecture, and that further performance improvement on the same platform is unlikely to change the scalability characteristics, especially when the number of rendering processors involved is large. The other contribution of this work is that we develop a unified framework to describe parallel compositing algorithms and show that two popular parallel compositing algorithms, binary swapping and parallel pipeline compositing, ar...

AbstractÐThis paper presents the design and performance of a new parallel graphics renderer for 3D images. This renderer is based on an adaptive supersampling approach that works for time/space-efficient execution on two classes of parallel computers. Our rendering scheme takes subpixel supersamples only along polygon edges. This leads to a significant reduction in rendering time and in buffer memory requirements. Furthermore, we offer a balanced rasterization of all transformed polygons. Experimental results prove these advantages on both a shared-memory SGI multiprocessor server and a Unix cluster of Sun workstations. We reveal performance effects of the new rendering scheme on subpixel resolution, polygon number, scene complexity, and memory requirements. The balanced parallel renderer demonstrates scalable performance with respect to increase in graphic complexity and in machine size. Our parallel renderer outperforms Crow's scheme in benchmark experiments performed. The improvements are made in three fronts: 1) reduction in rendering time, 2) higher efficiency with balanced workload, and 3) adaptive to available buffer memory size. The balanced renderer can be more cost-effectively embedded within many 3D graphics algorithms, such as those for edge smoothing and 3D visualization. Our parallel renderer is MPI-coded, offering high portability and cross-platform performance. These advantages can greatly improve the QoS in 3D imaging and in real-time interactive graphics. Index TermsÐComputer graphics, parallel rendering, supersampling, polygon rasterization, symmetric multiprocessors, cluster of workstations, MPI programming, load balancing, speedup and efficiency, and scalable performance.

We present e cient parallel algorithms for interactive display of higher order surfaces on current graphics systems. At each frame, these algorithms approximate the surface by polygons and rasterize them over the graphics pipeline. The time for polygon generation for each surface primitive varies between successive frames and we address issues in distributing the load across processors for di erent environments. This includes algorithms to statically distribute the primitives to reduce dynamic load imbalance as well a distributed wait-free algorithm for machines on which re-distribution is e cient, e.g. shared memory machine. These algorithms have been implemented on di erent graphics systems and applied to interactive display of trimmed spline models. In practice, we are able to obtain almost linear speed-ups (as a function of number of processors). Moreover, the distributed wait-free algorithm is faster by 25,30 % as compared to static and dynamic schemes. Keywords: Surface tessellation, Load balancing, Real-time rendering, Simulation-based

In this paper we describe a system, BOOLE, that generates the boundary representations (B-reps) of solids given as a CSG expression in the form of trimmed B'ezier patches. The system makes use of techniques from computational geometry, numerical linear algebra and symbolic computation to generate the B-reps. Given two solids, the system first computes the intersection curve between the two solids using our surface intersection algorithm. Using the topological information of each solid, it computes various components within each solid generated by the intersection curve and their connectivity. The component classification step is performed by ray-shooting. Depending on the Boolean operation performed, appropriate components are put together to obtain the final solid. We also present techniques to parallelize this system on shared memory multiprocessor machines. The system has been successfully used to generate B-reps for a number of large industrial models including parts of ...

This paper describes and experimentally evaluates three adaptive spatial subdivision heuristics for sort-first parallel graphics rendering on distributed-memory multicomputers. In sort-first rendering, imagespace, or screen, is divided into regions. Each processor is assigned one or multiple regions to render. Primitives in the scene are redistributed among the processors according to region assignments. The total number of primitives in the system may increase due to duplication of primitives crossing multiple regions assigned to different processors. The common characteristic of the algorithms discussed in this paper is that a 2-dimensional mesh is superimposed on the screen and screen is subdivided using the primitive distribution on this mesh. Each processor is assigned a single region to render. The first algorithm uses summed area table for subdividing the screen. The second algorithm uses quadtrees for subdivision. The third algorithm utilizes a graph partitioning...