ClearBoard

Summary

ClearBoard is an early exploration of what a shared digital workspace can be when it blends physical presence with computational drawing. Developed by Hiroshi Ishii and Minoru Kobayashi at NTT Human Interface Laboratories in the early 1990s, ClearBoard was designed to make remote collaboration feel as natural as talking and drawing together on a transparent surface. Its core metaphor — “talking through and drawing on a big transparent glass board” — guides a system where two people can draw and converse while maintaining eye contact, significantly reducing the cognitive and physical effort of switching attention between partner and workspace.

The technology uses a Drafter-Mirror architecture: cameras capture each participant’s drawing and posture while projectors display the partner’s contribution on the shared surface. This creates an illusion that collaborators are on either side of a transparent drawing plane, fostering a smooth blend of interpersonal communication and shared task focus. One of ClearBoard’s key findings was what researchers later called gaze awareness — the ability to perceive where a partner is looking and thus infer their focus of attention with greater precision than traditional remote tools allow.

ClearBoard was not just a tool; it was an early blueprint for interfaces that preserve body language, eye contact, gesture, and co-focus of attention — elements lost in many contemporary remote collaboration systems. By tightly coupling interpersonal space with shared workspace, ClearBoard pointed toward richer forms of mediated collaboration.

ClearBoard can be seen as one instance of the paradigm shift from traditional Human-Computer Interaction to Human-Human Interaction mediated by computers. We are interacting not with computers, but through computers. ClearBoard design is not only “beyond being there” but also a step beyond the traditional desktop metaphor based on a multiwindow interface. We expect ClearBoard to be useful both as a collaboration medium and as a vehicle to investigate the nature of dynamic human interaction Hiroshi Ishii

ClearBoard was the best thing I saw in the past 30 years after Doug Engelbart’s demo. Alan Kay

Key concepts

• Seamless shared workspace ClearBoard unifies interpersonal interaction and the shared drawing surface so collaborators don’t have to shift gaze or posture between task and partner.
• Transparent surface metaphor The system is centered on the metaphor of drawing and conversing through a transparent glass board, making the shared space feel physically continuous and natural.
• Gaze awareness Participants can more easily perceive where their partner is looking on the shared surface, strengthening non-verbal communication and shared attention during collaboration.
• Interpersonal and shared space integration ClearBoard’s design preserves social cues and body language while supporting collaborative content creation, anticipating future work in telepresence and real-time shared interfaces.

ClearBoard pioneered the idea that collaborative computing should preserve social presence — including eye contact, gestures, and shared focus — alongside shared digital content. By embedding collaborators into a single, continuous interaction surface, it anticipated later work in tangible and embodied interfaces, showing that “what we see together” can matter as much as “what we create together.”

This idea was originally published as ClearBoard: A Seamless Medium for Shared Drawing and Conversation with Eye Contact. It was later refined and expanded through a series of follow-up publications and follow-up experiments, see for example Integration of inter-personal space and shared workspace: ClearBoard design and experiments, Iterative Design of Seamless Collaboration Media, and Integration of interpersonal space and shared workspace: ClearBoard design and experiments.