ders: office text systems such as telex, computer supplies and digital TV. Of these three, it is the third which does seem to be the most likely. Paradoxically, that may help explain the seemingly slow acceptance of videotex which we referred to at the start of this article. Videotex lies in uncharted territory at the confluence of three hitherto

unrelated disciplines: publishing, digital inlorrnation technology (computers and telecommunications), and video. In the future these disciplines will inevitably conic together and the catalyst will be videote:,..

R. Woolfe

Siggraph '82 Bos ton , Massachuse t t s , USA, 2 6 - 5 0 Ju ly 1982

The largest and most well attended Siggraph conference ever, with over 20 000 conferees, brought together an excellent technical programme, a series of topical panels, an art show, cooperative sessions with the Eurographics Association, an exhibition, tutorials, films, and participants in what is becoming an annual call to the computer graphics equivalent of the Haj. It has become clear over the course of the past two years that the marketplace will not only support, but probably needs, two major shows for com- puter graphics.

Siggraph is so valuable because it is the venue for the release of the previous year's research by the ACM's members. This year one can divide the sessions into six major cate- gories of research: rendering techniques, standards, solid modelling, VLSI for graphics, systems and software, and panel discussions. The number of panels underwent an increase under Carl Machover's direction to include a presi- dent's forum, business graphics, standards, education and others. The largest art show to date wasprovided with a selective catalogue destined to become a collector's item. There was some additional work for the speakers who were attempting to attend both the Siggraph and the concurrent Harvard Computer Graphics Week in Cambridge, but delegates of the latter benefited from having access to the Siggraph exhibits.

Rendering The techniques used to produce images with computer graphics and image processing systems are a major area of study for Siggraph members. Jim Blinn's annual contribu- tions in this area approach the status of 'cult events' in the enthusiasm of his audience. This year he presented two papers - one which continues his research into the pro- cesses of light interacting with matter (on the statistical simulation of light passing through and being reflected by clouds of particles), and another on the use of ellipsoids in simulating human dynamics. The strength of his contribu- tion towards allowing more complete simulation of diffuse reflection provides us with ample room for speculation on what the feature films on space will look like. One of the problems addressed was how to allow for multiple reflec- tions and different amounts of shadowing from any direc- tion.

Norton and Rockwood provided a paper on their research into 'clamping', a mathematical function applied to texture functions. Texture is important in their application of simu- lation because it provides important cues in the determina- tion of height and motion. The clamping approach they

have developed solves the loss of texture to aliasing in an economic fashion, and provides for the sort of realistic simulation demonstrated in airport and ocean scenes shown at the film show. Goad, who is also working with simulation, described an algorithm for the removal of hidden surfaces. His approach is to construct each scene which depends upon the viewer's point of view. The result is an increase in efficiency for calculating such scenes.

Kawaguchi of Nippon Electric offered a paper describing his algorithm, 'Growth' (growth object work theorem) which is used to generate automatically certain natural forms: shells, horns, tusks, claws, and spiral plants. Along more traditional lines is the algorithm from Kajiya of Caltech. The formula is for ray tracing techniques to display bivariate polynomial surface patches.

Carlson, in one of several papers from Ohio State University, discussed an algorithm and data structure for three-dimen- sional object synthesis using surface patch intersections. The author reported that this is probably the first algorithm to support intersection surfaces for the animation environment. One application for the algorithm will be in modelling the human body to allow for the creation of joints. Color Image Quantization, written by Heckbert of NYIT was one of the more immediately practical presentations. The paper des- cribes research on high quality colour displays using small frame buffers (eight bits or less). He defines quantization as the task of sampling, selecting a colour map, remapping, and redrawing an image. Input for the research was done at 24 bits, and both popularity and median algorithms were used to redisplay the image. Both were shown to improve upon uniform quantization, and when coupled with dither- ing a high quality output can be produced, in a much more efficient fashion.

S tandards

The nature of Siggraph means that standards are a primary concern at the annual conference, and this year exceptionally so. The most important activity was the tacit agreement among speakers that the GKS graphics standard would be accepted by the ISO. Panel sessions on standards were valuable in involving the principals of the standards- making efforts - not only are they knowledgeable about conditions of the standards but are also aware of the state of their development or promulgation.

Solid mode l l ing

One of the most contentious issues in this area was address- ed in a paper by P. Hanrahan of the University of Wisconsin

58 DISPLAYS. JANUARY 1983