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HCI, Tech

Response to [Interacting with dynamically …] by Cao et al.


This paper explores the design space of using a hand-held projector and a passive pen in a large physical space. The main idea is the projector can be used as a torch and reveal partial details of a larger range of display. In this way, users can break the limit of small display while being able to view, select and edit them on any near-planar surface, ranging from a tabletop to a large wall. Based on this, a series of interaction techniques are presented including projector-only interaction and projector+pen interaction. When it comes to usages, the system allows single or multiple users, which is illustrated in a number of scenarios such as one controlling the projector to show slides while the other using the pen to navigate through them, one leaving a virtual note and the other finding the note later at the same place, etc.


Design principles:

  • Generic interaction schemes;
  • Applying real-world protocols:
  • Division and integration between projector and pen;
    • This is a very thoughtful consideration: “we deliberately assign tasks that are more global and coarse to the projector, and local and precise tasks to the pen”. Using complementary tools seem to solve most of the problems caused by any of them.
  • Supporting multiple people;
    • An extension to multi-person scenario seems to be a must.
  • Dynamically defining spaces.


The metaphor of using the projector like a torch (while the display seems to already exist in the space) is the “ah-ha” moment of this paper. However, stepping back, it seems to me more like a playful interaction system. A game scenario is certainly very compelling. But when it comes to, for instance, “I have an email” scenario, I could not help asking: how do you know you have an email while you are projecting on somewhere else? For another example, leaving a note on a physical bulletin board – using the projector seems more of a playful approach other than any way significantly better than, say, as simple as writing a real sticky note.

Having said that, I believe there are many more design possibilities using projectors, including at least the following two:

  • Related to Dominikus Baur’s project where he borrows large display to show visualization on mobile devices;
  • Identity-aware projector – such as projecting on a printer shows its internal structure or the instructions of using it.

About Xiang 'Anthony' Chen

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