Paul Rajlich
Research Programmer
Visualization and Virtual Environments
National Center for Supercomputing Applications
Collaborative Visualization on Very Large
High-Resolution Geographical Displays

Excerpts from the Operations Agreement with Boeing:

This project will investigate the use of high-resolution display systems for face-to-face (collocated) collaboration when analyzing and interpreting geographical data... This project will examine ways in which multiple users can concurrently interact with a Display Wall using portable nework devices such as palm top computers and tablet computers.

The Display Wall

The NCSA display wall that is being used for this project is made up of 40 (8x5) LCD projectors, each with XGA resolution (1024x768). The display is powered by a 49 node high performance graphics cluster: 1 head node, 40 display nodes (1 per projector), and 8 I/O nodes. The result is a display with an aggregate resolution of 8192x3840! The size and resolution of the display allows small groups of people to collaboratively examine incredibly detailed imagery.

Displaying Imagery

Given that there is a PC behind each projector, software is needed to make these PCs work together to create a seamless image across the tiles. Currently, we are using the NCSA Pixel Blaster from the NCSA Display-Wall-in-a-box distribution for this task. The NCSA Pixel Blaster handles the distribution of imagery data across the cluster and synchronization during display.


In order to display annotations, we have extended the functionality of the NCSA Pixel Blaster. Specifically, the application can receive annotation data over the network and overlay it on top of the imagery. Currently, the annotation is in the form of freehand strokes with varying color, thickness, and transparency. For instance, thin opaque strokes are similar in appearance to a pen and thick semi-transparent strokes are similar in appearance to a highlighting marker.

In the future, we plan to extend the annotation capabilities to include simple geometric primitives and text.

Multiple Imagery Sources

In addition, we have prototyped the display of subwindows and overlays for displaying multiple data sources concurrently. This functionality will either be integrated into the NCSA Pixel Blaster application, or a new application will be implemented from the ground up. Adding these features introduces a significant amount of complexity since the various imagery sources will likely be of different sizes, origins, and spacing. Ideally, the users in front of the display wall will be able to easily manipulate how the various layers of information are displayed on the wall. For instance, a user may want to overlay topo data on top of the base imagery, or create a moving subwindow where topo data is displayed instead of the base imagery.

Portable Network Devices

We have prototyped interfaces for handheld devices (Compaq iPaq) and tablet PCs.

The handheld is one of the devices that is used to control and annotate the imagery on the display wall. Designing an appropriate interface is a challenging task given the limited resolution of the handheld as compared to the incredible resolution of the display it is controlling. We are experimenting with several approaches.

Although the tablet is much higher resolution than the handheld device, it's resolution is still an order of magnitude less than the display wall. Therefore, for accurate annotation and navigation through data, a novel interface is still necessary. We are experimenting with several approaches.

(C)opyright 2003, Paul Rajlich       Want to see what I am doing now? Visit