No matter how powerful or elegant the technologies underlying multimedia computing, it is the user interface that ultimately determines how these systems will be used. We provide an overview of two emerging areas of user-interface research that will play major roles in future multimedia systems: virtual environments and ubiquitous computing. We discuss what they are and why they are important, and describe their relationship to current multimedia systems. While mouse and window-based user interfaces provide access to 2D graphics, video, and sound, virtual environments not only involve interactive 3D graphics, but further address all our senses through the use of spatial audio, haptics, and other modalities. While it is still a research goal to provide high-throughput video on demand, ubiquitous computing will require that multimedia network infrastructure also support extremely low-latency interaction among large numbers of mobile wireless users. To arrive at an understanding of the needs, capabilities, and potential of these new paradigms, we introduce their terminology and technology, and explain the basic system architectures being explored, leading up to a discussion of key current research issues and future directions.
