Tiled display walls provide a large-format environment for presenting high-resolution visualizations by tiling together the output from a collection of projectors. Multiple projectors allow display of images much larger than possible on standard computer display screens. The use of these walls enables researchers to step back and get an overall picture of a dataset or move in and study fine details without changing the visible image. For example, very high resolution satellite data sets can be displayed as a single image. In addition, the large display screen can be blocked and used to display images from multiple sources such as ensemble model simulations or current weather data.

The use of large display walls for various applications in meteorology, oceanography, and hydrology is being explored at the National Center for Supercomputing Applications (NCSA). This includes the applications mentioned in the preceding paragraph. The wall in use was recently designed and installed by the NCSA's Visualization and Virtual Environments group. Currently, it is 20-tile scalable display wall that provides a display surface that is 4096 x 3840 pixels, useful for showing high-resolution imagery and animations, or for showing multiple information sources side-by-side. At 12 feet across and 9 feet high, the Wall easily accommodates small teams of people working together.

A 20-node PC Linux cluster is used to drive the display wall. The machines are dual-processor HP Kayaks, running at 550 MHz, with GeForce2 graphics accelerator cards, and communicating over Myrinet. The machines are connected to a collection of 20 NEC VT540 projectors, arranged in a matrix 5 high and 4 across. The output of the NECs is rear-projected towards a single screen, creating a large-format, high-resolution image space. The wall will be scaled to 40 tiles later this year with a resolution of 8192 x 3840 (or 8 tiles wide by 5 tiles tall). Costs for the facility are controlled by using commodity projectors and low-cost PCs.

In order to enable others to more easily set up walls, the NCSA Alliance has launched the DisplayWall-in-a-Box effort. This is a collaborative effort with contributions from Argonne National Laboratory, University of Utah, University of Illinois at Urbana-Champaign, University of Minnesota, Princeton University, Stanford University, and the National Center for Supercomputing Applications. It provides guidelines for building a tiled display wall, along with a collection of software for displaying imagery on the wall. The DisplayWall-in-a-Box software toolkit includes utilities and applications for single and multiple image display, movie playback, and image roaming as well as complete visualization tools that can direct output to a tiled wall. Further information can be found http://www.ncsa.uiuc.edu/TechFocus/Deployment/DBox/index.html.