Thursday, November 16, 2006
Monday, August 22, 2005
Rabin's PhD
I first met Rabin Ezra some time in the second half of the 1980s. I taught the Computer Graphics course, a final year course at Queen Mary and
During the course itself I had several after-class discussions with him, and it was during one of these that the issue of his staying on to do a PhD arose. He was very interested in hardware for real-time computer graphics. Also I had read a very interesting paper by some people at Sun Microsystems that provided a very efficient method for the rendering of curves and surface that would be amenable to hardware implementation. Rabin became interested in this and we agreed upon this as his topic. He started the PhD probably in 1988.
He made rapid progress and actually soon had a hardware design for the main part of the surface generation graphics hardware. He passed his first and second year vivas without trouble. But then he did run into trouble. It seemed to be a trivial problem. Suppose you are given n points in 3D space. You need to decide if all these points are approximately on a plane. Mathematically this is not difficult. Take any three of the points that are not themselves on a straight line, and from these find the equation of the plane that passes through them. Then for each of the remaining points find their distance from this plane, and if the maximum distance of all these points from the plane is less than a certain fixed and given tolerance, then we can say that ‘approximately’ (how approximate depends on the chosen tolerance) the points are flat, i.e., are on a plane. Mathematically this is trivial. Transforming it into an efficient and accurate computer program is less trivial. Fitting it into a hardware design architecture so that it doesn’t become a major bottleneck is very difficult. This is what occupied Rabin for the remainder of his PhD. Finding some workable solution to this problem took about 2 years.
In January 1991 I took sabbatical leave from QMW to take a Visiting Professorship at
I was offered additional semesters (this time paid) by
During this period Rabin and I had agreed that he would begin writing his PhD. One day shortly after I had returned to Berkeley Rabin sent me an email: “I’ve finished!”. I was very surprised. A PhD thesis normally runs to about 150 pages. Had he written so much, with all the references and all the figures, in such a short time? I asked him to send me the thesis. Well what he had written was fine – but it was about 40 pages in length. He had succinctly stated the problem, and the solution and results, in as terse manner as possible. There was nothing at all wrong with it, except that it really was too terse. So over the next year or so we gradually got more and more flesh put on the bare bones of the thesis. It was somehow against Rabin’s nature to spell things out in detail. “It’s obvious” he would say, "why should I have to write about it?" Well, obvious to him, and to me, but to the examiners, and other readers? – not so obvious. Yes, things have to spelled out, in detail. Where does this equation come from? Why is this statement true? What reference do you have to back up this idea? With some resistance Rabin eventually saw the light. But in a way of course Rabin was right. He had stated the problem and given the solution and results. Really of course the rest is convention. This is how a PhD is supposed to look. To be awarded a PhD he had to learn to follow certain conventions. But … they are only conventions.
He finally submitted in late 1993 or early 1994. The thesis length was still quite short, but acceptable.
On the day of the viva he was extremely nervous, to the point of shaking visibly – Rabin was not one for formally speaking in public, and he would have to do a short presentation in front of the two examiners. I told the examiners about his state. One of whom was Dr Simon Arridge from University College London who said I should tell Rabin not to worry, everything was ok. This did seem to quieten his nerves somewhat, and although still visibly shaking when he did his presentation, he got through it well. In the ensuing viva period he relaxed and engaged in genuine discussion with the examiners, and nothing remarkable happened. He was awarded the PhD.
After the award of the PhD Rabin went to work for Canon Research Europe where he specialised in graphics hardware and software, and especially on the interface between the two. CRE was partially founded by an ex-QMW student, and a number of ex-QMW people eventually worked there.
I kept in touch with Rabin over the years, and in particular used to meet him annually at the SIGGRAPH meeting in the
Rabin is unforgettable. Although I will never see him physically again, he is still around. Although he passed away before SIGGRAPH 2005, I believe that he was still there, and enjoyed it as usual. He lives on at least through our memories and in our hearts.