A User Study on Curved Edges in Graph Visualization

Abstract

Abstract-Recently there has been increasing research interest in displaying graphs with curved edges to produce more readable visualizations. While there are several automatic techniques, little has been done to evaluate their effectiveness empirically. In this paper we present two experiments studying the impact of edge curvature on graph readability. The goal is to understand the advantages and disadvantages of using curved edges for common graph tasks compared to straight line segments, which are the conventional choice for showing edges in node-link diagrams. We included several edge variations: straight edges, edges with different curvature levels, and mixed straight and curved edges. During the experiments, participants were asked to complete network tasks including determination of connectivity, shortest path, node degree, and common neighbors. We also asked the participants to provide subjective ratings of the aesthetics of different edge types. The results show significant performance differences between the straight and curved edges and clear distinctions between variations of curved edges.

On the Usability of Lombardi Graph Drawings

“…al [19] also showed no performance difference between Lombardi and straightline drawings, although, contrary to our results, their participants demonstrated an overwhelming preference for straight-line graphs.…”

Using Eye Tracking to Evaluate the Usability of Flow Maps

“…They failed to obtain correct answers in maps using straight lines. This result is consistent with previous findings that overlapping or intersecting features may cause a decrease in task correctness [1,21]. Thus, maps using straight lines lead to a lower effectiveness than maps using curves.…”

“…As the results of finish time show (Table 3 and Figure 3), the maps using curved features to represent the flow direction were significantly less efficient, which is a result similar to the findings of previous studies [21,22]. In our experiment, finish time reflects the average time that participants used in determining the directions of flows, comparing the volumes of flows, and judging the correct answers in one task.…”

“…Scholars have produced different findings with regard to this issue. Xu et al [21] conducted a user study of curved edges in graph visualization. They asked participants to complete network tasks, including the determination of connectivity, shortest path, node degree, and common neighbors, and to provide subjective ratings of the aesthetics of different edge types.…”

Drawing Trees with Perfect Angular Resolution and Polynomial Area

“…Löffler and Nöllenburg [25] showed that all outerpaths, i.e., outerplanar graphs whose weak dual is a path, have an outerplanar Lombardi drawing. In terms of the usability of Lombardi drawings, two independent user studies [27,32] examined the performance of Lombardi versus straight-line drawings for several graph reading tasks. While the study of Purchase et al [27] showed an advantage of straightline drawings for two out of three tasks, but aesthetic preference for Lombardi drawings, the study of Xu et al [32] did not show significant performance differences between the two types of drawings, but a strong aesthetic preference for straight-line drawings.…”