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Technology studies and the user-oriented 'wing' of computer science have largely shared a 'heroic', albeit critical, vision of computer system design: that designers inscribe particular views of the user, user activities and priorities into the artefact, but these are often 'the wrong values', based on an inadequate or misleading view of the user and their(More)
a dissertation submitted to the program in scientific computing and computational mathematics and the committee on graduate studies of stanford university in partial fulfillment of the requirements for the degree of doctor of philosophy ii I certify that I have read this dissertation and that in my opinion it is fully adequate, in scope and in quality, as a(More)
A new surface radiance model for diiuse lighting is presented which incorporates shadows, interreeections, and surface orientation. An algorithm is presented that uses this model to compute shape{from{shading under diiuse lighting. The algorithm is tested on both synthetic and real images, and is found to perform more accurately than the only previous(More)
The layout of large scenes can be a time–consuming and tedious task. In most current systems, the user must position each of the objects by hand, one at a time. This paper presents a constraint–based automatic placement system, which allows the user to quickly and easily lay out complex scenes. The system uses a combination of automatically– generated(More)
Graphics hardware has been developed with image production in mind, but current hardware can be exploited for much more general computation. This paper shows that graphics hardware can perform general calculations, which accelerate the rendering process much earlier than at the latter image generation stages. An example is given of the real time calculation(More)
We present empirical studies that consider the effects of stereopsis and simulated aerial perspective on depth perception in translucent volumes. We consider a purely absorptive lighting model, in which light is not scattered or reflected, but is simply absorbed as it passes through the volume. A purely absorptive lighting model is used, for example, when(More)
—It is widely known that real nonminimum phase zeros lead to step response undershoot, and that the size of the undershoot necessarily tends to infinity as the settling time tends to zero. In this note, we show that the presence of two or more real nonminimum phase zeros can lead to step response overshoot in addition to undershoot. A lower bound on the(More)