Algorithms and Bounds for Overloaded Orthogonal Drawings

Abstract

Orthogonal drawings are widely used for graph visualization due to their high clarity and ease of representation. But when it comes to high-degree and massive graphs, even orthogonal drawings have difficulties producing a clean and simple visualization. In this paper we present a technique called Overloaded Orthogonal Drawing that greatly improves the readability by proposing a new vertex placement and reframing the orthogonal edge routing approach. We first place the vertices on grid points following a relaxed version of dominance drawing, called weak dominance condition. Edge routing is implied automatically by the vertex coordinates. In order to simplify these drawings we use an overloading technique of the edges. All algorithms are simple and easy to implement and can be applied to directed acyclic graphs, planar, non-planar and undirected graphs. We also present bounds on the number of bends and the area. Overloaded orthogonal drawings present several interesting properties such as efficient visual edge confirmation as well as clarity of the drawing.