A system that allows people to simultaneously modify a common design in a graphically rich environment was developed to identify and examine groupware interface issues unique to three-dimensional computer-aided design. Experiments confirmed that a simultaneous mode of edit access is preferred over a turn-taking mode for two-person interactions. Also, independent points of view (e.g., isometric versus top view) between designers optimized parallel activity. Further experiments that aimed to transfer software-usage knowledge through the groupware system led to the development of the viewpoint. The viewpoint is a tool that indicates the points of view of different designers as well as provides a method of pointing effective in an environment where arbitrary, contrasting points of views are allowed. KEYWORDS Computer-aided design, graphics, three-dimensional.