We show that every graph G with maximum degree three has a straight-line drawing in the plane using edges of at most five different slopes. Moreover, if G is connected and has at least one vertex of degree less than three, then four directions suffice.
Ali H. Sayed, Mert Kayaalp, Valentina Shumovskaia, Mert Cemri
Etienne Michel François Bamas, Lars Rohwedder