Wednesday, July 31, 2019

Tribute to Godfried by Joseph O'Rourke

I met Godfried at a pattern recognition conference around 1980, and he invited me to McGill to give a talk. It was there that he introduced me to art gallery theorems. I immediately abandoned my pattern recognition work and focused on art galleries, with considerable help from Godfried. For example, it was his idea to generalize guards to mobile guards, patrolling an edge. And, as Joe Mitchell mentions, he introduced what has become known as GFP, “Godfried’s Favorite Polygon,” to show that the boundary can be completely covered by vertex guards while leaving interior points invisible:

A few characteristics:

  •  He loved counterexamples such as the GFP, and in fact several of his papers have the title, “A counterexample to …”
  • He was a scholar par excellence: he read everything, and had a near photographic memory. His bibliographies were always extremely long.
  • He was immensely creative in finding rich research areas for his beloved Bellairs workshops. Even at this past March’s workshop he raised a question asking for the probability that a 4-bar linkage is Grashof.
  • He was a great and fast writer. Once at one of his Bellairs workshops, on the final day when everyone was milling around, he sat down and penned (literally penned) a paper from start to finish. And his first drafts were only epsilon from final drafts.
  • As Jit mentioned, he insisted on the broadest possible notion of collaboration, instituting the rule that everyone at his workshops was by default a co-author on every paper (all listed alphabetically), unless they withdrew their name. The CompGeom community to this day continues Godfried’s tradition of collaboration.
  • He had a great sense of humor, introducing (in Barbados of course) sail polygons, crab polygons, and palm polygons:

He truly is the father of computational geometry, co-starting both SoCG (with me) and CCCG (with David Avis).
He changed my life by introducing me to CompGeom, and then mentoring me for nearly forty years. May we all strive to follow the high standards he set for our community, for in that way Godfried lives on.