Shared ClearBoard

by Andrew Begel
CS294-7 Project Proposal
10/30/97

Problem

The MASH Media Board allows people to write and draw onto a shared workspace that every person in a video conferencing session can access. However, it provides us with only a limited palette since any information presented must be copied into it from the application where we developed the material. Since the goal of presenting information is to prepare it once and show it to everyone, this act of copying inevitably degrades the quality of the information. For example, MB can't display multiple fonts, doesn't handle line wrapping, and doesn't support easy importation of graphics, which are all the things that make or break a presentation. As an annotation tool, the MB is great because anyone can write something at any time or illustrate a point by drawing a circle around something.

Analysis

I'd like to combine the good qualities of annotation with a direct manipulation style of information presentation. I'd like to create a "network lens" that would ride on top of any particular display and would transmit its data to other people in the session. In addition, the tool would support annotation tools, like text writing and drawing on top of the display. This way, if you need to present something from Netscape, you can just move the lens over Netscape, and start talking. You could illustrate points by circling things in the lens and these updates would be transferred to the audience. The final concept is something similar to a Media Board application with a transparent background.

Suggested Design

There have been some designs for "magic lenses" in the past. These lenses have been typically used to scale images (magnify images for people with bad vision), but they have also been used to filter information. A group of researchers at U. Toronto, U. Washington and Xerox PARC created this new style of see-through interface with Toolglass and Magic Lenses in 1993. They created lenses of arbitrary size and shape that could be used on a display to filter information. For example, they had a fractal lens, which fractalized any image it was passed over. They had a magnification lens that magnified what was under it. There were color shift filters, symmetry filters, information annotation filters, etc.

This application would be similar to these magic lenses, but would transmit its "vision" over an RTP multicast network to many people. Presumably this could use the scalable reliable multicast protocol created by Steve McCanne and Teck-Lee Tung. In addition, drawing and writing tools would be added, a la Media Board, to allow the user to annotate the vision.

I envision this to be a minimalist application. One would only need a small palette of tools, a display lens, and a context switching button (allowing the user to click "through" the transparency to the applications below). It is advantagous to let the user manipulate the actual computer stuff underneath the drawing surface. Toolglass invented transparent buttons that would allow mouse clicks to "pass" through to the application beneath them. While this is a nice goal, a more reasonable approach would be to make this system exist in two modes, one where you could manipulate the computer underneath the lens, and another where you could draw and write on top of the lens.

I would like to implement this in Tcl/Tk/X Windows (as I don't have a PC handy, nor do I want to figure out the entire Win32 API in a month). I can borrow ideas from Xeyes (which has a transparent window and draws stuff on top of it) and wscrawl, a program which implements a simple whiteboard. Once these two features are integrated, all that would remain would be to attach it to some network protocol (either X or SRM) to transmit the info to everyone's screens.

Experiment

A complex user study involving hundreds of users and hetergenous working environments would be great, but realistically, in four weeks, I might be able to test this once in the CoLab during a class. I'd envision using the LiveBoard in BSD UNIX mode to run the app and have remote people running the client instead of Media Board.

I anticipate several UI issues which would be brought out by using the application. What kind of palette should be used? How can it be attached to the drawing layer without getting in the way? How will users control what is sent over the network? What happens if the underlying screen is undergoing animation? What will happen to any drawings that are on top of it? What happens when the user moves the underlying application (let's say Netscape) over to the left 10 pixels. Does the drawing layer move? Perhaps it should be movable by the user? Or scrollable? All these design decisions could be easily decided with a small prototype.

Grading Contract

Assurance of Feasibility: B-
Implementation of transparent white board (non-networked): B
Connection of transparent white board to SRM or X: A-
Running through one design/rewrite iteration: A+

Andrew Begel
abegel@cs.berkeley.edu