A practical approach for 1/4-SHPEDs

Avoiding crossings for reducing visual clutter is one of the main objectives in the area of graph drawing. Apart from work on geometric solutions to this problem, there are radical approaches originating from information visualization in which edges are drawn just partially. Theory on this approach is already established in several directions and 1/4-SHPED arose as standard. A 1/4-SHPED (Symmetric Homogeneous Partial Edge Drawing) is a drawing model in which vertices are drawn as points and edges as two pieces (= stubs) of a straight-line segment, each incident to a vertex, without any crossing stubs, and with stub size 1/4 of the total edge length. If crossings are permitted in a 1/4-SHPED, we call it 1/4-nSHPED (n = nearly). 1/4-nSHPEDs and 1/4-SHPEDs help the reader inferring adjacent vertices by approximating the distance due to four times the stub length. Symmetry of stubs helps to verify adjacency. We describe a force-directed algorithm that aims at producing a 1/4-SHPED. The algorithm is finally evaluated with several classes of graphs.