Virtual reality technology is increasingly being applied to globally distributed teams engaged in collaborative product design. Observations of product design teams have suggested four distinct patterns of collaboration— complementary, competitive, peer-to-peer , and leader-follower. Another insight from observation is that collaboration consists of fluid transitions between these patterns in the accomplishment of the design task, driven by a flexible process of subgrouping and regrouping which reflects the structure and progress of the task. Yet most collaborative virtual environment systems support only one pattern of collaboration—peer-to-peer—and those that do explicitly support multiple patterns or roles do not allow fluid transitions between them in the context of the same task. In addition, no explicit support is provided to allow subgroups to be formed and dissolved. A collaborative virtual environment that supports multiple collaboration patterns and fluid transitions was developed using the Shared Simple Virtual Environment (SSVE) application framework. A novel user interface widget, the collaboration tree , was created to drive the subgrouping and regrouping process. Group experiments were performed to test the operating hypothesis that support for group collaboration patterns led to higher performance. The result was that the operating hypothesis was confirmed; however, the conceptual approach to problem solving, suggested by the presence of support for collaboration patterns, may have been more significant than the actual mechanism provided.

As collaboration in virtual environments becomes more object-focused and closely coupled, the frequency of conflicts in accessing shared objects can increase. In addition, two kinds of concurrency control “surprises” become more disruptive to the collaboration. Undo surprises can occur when a previously visible change is undone because of an access conflict. Intention surprises can happen when a concurrent action by a remote session changes the structure of a shared object at the same perceived time as a local access of that object, such that the local user might not get what they expect because they have not had time to visually process the change. A hierarchy of three concurrency control mechanisms is presented in descending order of collaborative surprises, which allows the concurrency scheme to be tailored to the tolerance for such surprises. One mechanism is semioptimistic; the other two are pessimistic. Designed for peer-to-peer virtual environments in which several threads have access to the shared scene graph, these algorithms are straightforward and relatively simple. They can be implemented using C/C++ and Java, under Windows and Unix, on both desktop and immersive systems. In a series of usability experiments, the average performance of the most conservative concurrency control mechanism on a local LAN was found to be quite acceptable.