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Creating, Connecting and Collaborating through Computing, International Conference on (2005)
Kyoto, Japan
Jan. 28, 2005 to Jan. 29, 2005
ISBN: 0-7695-2325-0
pp: 50-56
David Smith , Croquet Project, Cary NC
Andreas Raab , Hewlett Packard Laboratories, Palo Alto, CA
Yoshiki Ohshima , Twin Sun, Inc., El Segundo, CA
David P. Reed , Hewlett Packard Laboratories, Cambridge, MA
Alan Kay , Hewlett Packard, Glendale, CA
Croquet is a collaborative 3D platform that allows users to work together to create and share ideas. From the beginning we have worked to ensure that the Croquet interface remain as modeless as possible. This allows the user to be most productive with the fewest errors. This is even more important in a collaborative 3D environment. The modeless nature of Croquet has allowed us a great deal of flexibility in how the user is able to both move around the environment while easily manipulating it. Certain kinds of applications, however, require some degree of intelligent pseudo-modal behavior. An example is using a CAD system to create new objects. This process forces the user into an object-creation/modification "mode" that can take control of the interface for a short duration. E.g. we might be in the "line drawing" mode. Clearly this is not a problem, but we also need to ensure that we do not get trapped by the CAD application itself. In a sense, it should have the same degree of "mode" as drawing the line. Our approach to ensuring that Croquet remains modeless is to utilize filter portals that modify both the views of the data in the 3D space and the actions that the user makes through these filter portals.<div></div> We are developing an architecture that incorporates the ideas of filters and controls for 3D to solve this problem. Our model uses the Croquet 2D portals as view filters that can modify the nature of the content displayed on the other side of the filter. It also uses these view portals to act to translate the users actions and maintain the editing mode. This allows "through the 3D window" editing of shared content.<div></div> Another problem is that this collaborative sharing of interfaces tends to be complex. A new approach to this, an extension of the model-view-controller approach pioneered in Smalltalk, is described. This extension of MVC to collaborative 3D user interface design consists of interactors, tasks, and replicants. This architecture solves the collaboration UI problem in a way that makes it quite easy for the designer to create robust multi-user applications without having to manage the divergent states and goals of each user. The programmer can focus on the design of an extensible system as if he is dealing with a single user.

Y. Ohshima, A. Raab, D. P. Reed, A. Kay and D. Smith, "Filters and Tasks in Croquet," Creating, Connecting and Collaborating through Computing, International Conference on(C5), Kyoto, Japan, 2005, pp. 50-56.
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