On Monotone Drawings of Trees

Kindermann, Philipp and Schulz, André and Spoerhase, Joachim and Wolff, Alexander (2014) On Monotone Drawings of Trees. In: Graph Drawing 22nd International Symposium, GD 2014, September 24-26, 2014 , pp. 488-500(Official URL: http://dx.doi.org/10.1007/978-3-662-45803-7_41).

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A crossing-free straight-line drawing of a graph is monotone if there is a monotone path between any pair of vertices with respect to some direction. We show how to construct a monotone drawing of a tree with n vertices on an O(n 1.5) ×O(n 1.5) grid whose angles are close to the best possible angular resolution. Our drawings are convex, that is, if every edge to a leaf is substituted by a ray, the (unbounded) faces form convex regions. It is known that convex drawings are monotone and, in the case of trees, also crossing-free. A monotone drawing is strongly monotone if, for every pair of vertices, the direction that witnesses the monotonicity comes from the vector that connects the two vertices. We show that every tree admits a strongly monotone drawing. For biconnected outerplanar graphs, this is easy to see. On the other hand, we present a simply-connected graph that does not have a strongly monotone drawing in any embedding.

Item Type: Conference Paper
Additional Information: 10.1007/978-3-662-45803-7_41
Classifications: G Algorithms and Complexity > G.560 Geometry
G Algorithms and Complexity > G.070 Area / Edge Length
G Algorithms and Complexity > G.999 Others
P Styles > P.540 Planar
P Styles > P.720 Straight-line
Z Theory > Z.250 Geometry
URI: http://gdea.informatik.uni-koeln.de/id/eprint/1457

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