Kei Yuasa

Computation and performance issues In coliseum: an immersive videoconferencing system

Coliseum is a multiuser immersive remote teleconferencing system designed to provide collaborative workers the experience of face-to-face meetings from their desktops. Five cameras are attached to each PC display and directed at the participant. From these video streams, view synthesis methods produce arbitrary-perspective renderings of the participant and transmit them to others at interactive rates, currently about 15 frames per second. Combining these renderings in a shared synthetic environment gives the appearance of having all participants interacting in a common space. In this way, Coliseum enables users to share a virtual world, with acquired-image renderings of their appearance replacing the synthetic representations provided by more conventional avatar-populated virtual worlds. The system supports virtual mobility--participants may move around the shared space--and reciprocal gaze, and has been demonstrated in collaborative sessions of up to ten Coliseum workstations, and sessions spanning two continents. This paper summarizes the technology, and reports on issues related to its performance.

Texture tile visibility determination for dynamic texture loading

Three-dimensional scenes have become an important form of content deliverable through the Internet. Standard formats such as Virtual Reality Modeling Language (VRML) make it possible to dynamically download complex scenes from a server directly to a web browser. However, limited bandwidth between servers and clients presents an obstacle to the availability of more complex scenes, since geometry and texture maps for a reasonably complex scene may take many minutes to transfer over a typical telephone modem link. This paper addresses one part of the bandwidth bottleneck, texture transmission. Current display methods transmit an entire texture to the client before it can be used for rendering. We present an alternative method which subdivides each texture into tiles, and dynamically determines on the client which tiles are visible to the user. Texture tiles are requested by the client in an order determined by the number of screen pixels affected by the texture tile, so that texture tiles which affect the greatest number of screen pixels are transmitted first. The client can render images during texture loading using tiles which have already been loaded. The tile visibility calculations take full account of occlusion and multiple texture image resolution levels, and are dynamically recalculated each time a new frame is rendered. We show how a few additions to the standard graphics hardware pipeline can add this capability without radical architecture changes, and with only moderate hardware cost. The addition of this capability makes it practical to use large textures even over relatively slow network connections.

Governing the contract lifecycle: a framework for sequential configuration of loosely-coupled systems

Sequential configuration is a fundamental pattern that occurs when integrating systems that span domains and levels of abstraction. This task requires the integration of heterogeneous autonomous information systems, processes, and applications. We propose an extensible system for correlating sequential configurations across loosely-coupled systems. Our framework defines fundamental abstractions and interfaces that enable the implementation of domain-specific models. We build upon our framework to provide a suite of tools to support applications that manage the configuration lifecycle. Our implemented prototype application integrates the processes, tools, and data involved in the first two stages of the IT outsourced services contract lifecycle.

Enabling outsourced service providers to think globally while acting locally

Enterprises commonly outsource all or part of their IT to vendors as a way to reduce the cost of IT, to accurately estimate what they spend on IT, and to improve its effectiveness. These contracts vary in complexity from the outsourcing of a world-wide IT function to smaller, country-specific, deals.