Showing papers by "Kai Li published in 2000"

Building and using a scalable display wall system

Abstract: Princeton's scalable display wall project explores building and using a large-format display with commodity components. The prototype system has been operational since March 1998. Our goal is to construct a collaborative space that fully exploits a large-format display system with immersive sound and natural user interfaces. Our prototype system is built with low-cost commodity components: a cluster of PCs, PC graphics accelerators, consumer video and sound equipment, and portable presentation projectors. This approach has the advantages of low cost and of tracking technology well, as high-volume commodity components typically have better price-performance ratios and improve at faster rates than special-purpose hardware. We report our early experiences in building and using the display wall system. In particular, we describe our approach to research challenges in several specific research areas, including seamless tiling, parallel rendering, parallel data visualization, parallel MPEG decoding, layered multiresolution video input, multichannel immersive sound, user interfaces, application tools, and content creation.

Hybrid sort-first and sort-last parallel rendering with a cluster of PCs

Abstract: 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, view-dependent 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.

Automatic alignment of high-resolution multi-projector display using an un-calibrated camera

Abstract: A scalable, high-resolution display may be constructed by tiling many projected images over a single display surface. One fundamental challenge for such a display is to avoid visible seams due to misalignment among the projectors. Traditional methods for avoiding seams involve sophisticated mechanical devices and expensive CRT projectors, coupled with extensive human effort for fine-tuning the projectors. The paper describes an automatic alignment method that relies on an inexpensive, uncalibrated camera to measure the relative mismatches between neighboring projectors, and then correct the projected imagery to avoid seams without significant human effort.

Trading capacity for performance in a disk array

Abstract: A variety of performance-enhancing techniques, such as striping, mirroring, and rotational data replication, exist in the disk array literature. Given a fixed budget of disks, one must intelligently choose what combination of these techniques to employ. In this paper, we present a way of designing disk arrays that can flexibly and systematically reduce seek and rotational delay in a balanced manner. We give analytical models that can guide an array designer towards optimal configurations by considering both disk and workload characteristics. We have implemented a prototype disk array that incorporates the configuration models. In the process, we have also developed a robust disk head position prediction mechanism without any hardware support. The resulting prototype demonstrates the effectiveness of the configuration models.

Large-format displays

Abstract: magine a future when every surface in every built space is a high-resolution active display with sensing capabilities. Scenario: I'm walking down the hall toward my office when I'm reminded that I'm late for a meeting with Mary to discuss the design of the students' center being built on campus. Unsure of the location of her office, I tap on the wall next to me and a large floorplan appears. After following a path displayed on the floor to guide me, I arrive at her office, and we begin to work. Mary and I view an immersive walkthrough of the design on her \" smart wall, \" and I draw modifications with a virtual marker, whose strokes are recognized and used to manipulate the computer model … Scenarios like this one are no longer science fiction— the technologies to make interactive display surfaces commonplace are being invented and deployed right now. Soon we will move into a new era of computing— ubiquitous visual computing based on enormous visual information and natural user interactions. The reasons for this new era are twofold: increased computer performance and developed display techonology. First, continuous rapid improvements in CPU performance , storage density, and network bandwidth have provided sufficient bandwidth and computational resources to support high-resolution displays and natural human-computer interactions. Nowadays, the main bandwidth bottleneck in an interactive computer system occurs in the link between computer and human, not between computer components within the system. Second, large-format display devices, such as projectors and flat panels, are rapidly becoming commodity items. Meanwhile, new display technologies, such as organic light-emitting diodes (OLED), will soon become available at inexpensive prices. They can be attached to almost any kind of surface, allowing unlimited freedom of design for the interiors and exteriors of rooms and buildings. We believe that new display technologies will revolutionize the way we use computers, making us rethink the relationship between information technology and our society. As an example, consider how wall-sized displays enable qualitatively different human-computer interactions than traditional desktop displays. A recent paper by Mayer divides viewing experience into four categories. 1 The first category is the \" postage-stamp experience, \" where the field of view is constrained by desktop system bandwidth limitations and display technology limitations. The second is the \" television experience. \" Television is ubiquitous and it's the baseline of multimedia applications on a digital computer. The third is the …

Sort-First Parallel Rendering with a Cluster of PCs

Abstract: The objective of our research is to investigate whether it is possible to construct a fast and inexpensive parallel rendering system leveraging the aggregate performance of multiple commodity graphics accelerators in PCs connected by a system area network. We investigate a sort-first approach [1, 2, 3]. As shown in Figure 1, our system comprises of a client PC, servers PCs, and a display PC arranged in a three-stage pipeline. During the first stage, the client partitions the screen into tiles and assigns each of them to a different server. During the next stage, every server renders all the graphics primitives at least partially overlapping its assigned tile from a replicated scene database to form a subimage and sends the resulting pixels to the display PC. Finally, the display PC composites all the subimages in its frame buffer for display. The main challenge is to develop a dynamic screen partitioning algorithm that balances the rendering load among the servers, minimizes overheads by reducing primitive-tile overlaps, and executes at interactive rates. Our method is based on the mesh-based adaptive decomposition (MAHD) algorithm described by Mueller [2]. Since it is not possible for the client PC to transform and sort every graphics primitive among the tiles, we group primitives into coarse-grained objects. The client partitions the screen based on the predicted rendering costs of these objects, while the servers perform the detailed sorting for each image using the bounding volume hierarchy as they render objects. The key idea is that the client and servers share the costs of sorting graphics primitives among tiles, with the major portion of the sorting done in parallel by the servers. To test the effectiveness of our sort-first approach, we have implemented a prototype system

Next-generation visualization displays: the research challenges of building tiled displays (panel session)

Abstract: Tiled displays (multiple projector arrays) are quickly becoming technologically viable options for constructing high-end displays at a reasonable cost. Tiled displays address the need for increased resolution, increased field of view, large-scale form factor for group-oriented visualization and provide possible mechanisms for scaling graphics performance and leveraging commodity technologies. Numerous research groups are currently investigating tiled display technologies and their use in visualization applications. While tiled displays have a lot of potential to offer the visualization community, there are still many open research questions that limit their adoption. This panel will discuss the current state-of-the-art and open research issues related to tiled displays in the areas of applications, compute systems, display surfaces, projectors, and overall architecture of complete systems. Some of the questions that will be addressed include: