Drawing planar graphs of bounded degree with few slopes
arXiv:1009.1315
Abstract
We settle a problem of Dujmović, Eppstein, Suderman, and Wood by showing that there exists a function with the property that every planar graph with maximum degree admits a drawing with noncrossing straight-line edges, using at most different slopes. If we allow the edges to be represented by polygonal paths with {\em one} bend, then 2d slopes suffice. Allowing {\em two} bends per edge, every planar graph with maximum degree can be drawn using segments of at most different slopes. There is only one exception: the graph formed by the edges of an octahedron is 4-regular, yet it requires 3 slopes. These bounds cannot be improved.