Graph Drawing Contest Report

This year, the Graph Drawing Contest was again divided into two parts, as was usual for the past years: the creative topic and the live challenge.

Following the last two editions, this year’s creative contest focused on only one dataset. The creative topic was Dark: a German sci-fi thriller about time travel, fate, and family secrets. The dataset consists of events in the series, characters involved in each event, and some additional information per event (as described below). The contestant are invited to explore the intricate relationships between events, characters, and timelines in Dark. The data set was published about half a year in advance, and contestants submitted their visualizations before the conference started.

The live challenge took place during the conference in a format similar to a typical programming contest. Teams were presented with a collection of challenge graphs and had one hour to submit their highest scoring drawings. Since the topic had remained the same for the last two years, we introduced a new optimization problem this year: given an undirected simple graph and a grid, find a straight-line drawing with vertices placed on grid points, such that the drawing is $k$-planar for as low a $k$ as possible.

Overall, we received 34 submissions: 12 submissions for the creative topics and 22 submissions for the live challenge (14 manual and 8 automatic).

The dataset for the Creative Topic represents the events of the Netflix show Dark. We provided a directed graph, in which each event forms a vertex and edges represent cause and effect relationships between events.

Each vertex and edge is enriched with some metadata to flesh out the events and the relationships between them. Like last year, we explicitly asked contestants to formulate a question or hypothesis about the data and try to answer or explore it with their visualization.

Vertices have an ID, a Description, and a Date. The date is especially important since time travel plays an important role in Dark. Furthermore, we provide a list of Characters that are involved in an event. We added some additional metadata about whether a character dies and/or whether an event is a pivotal moment in the story. Finally, as the show progresses, the characters find out there are multiple parallel worlds, so for each event we explicitly state which World it takes place in. This lead to the following features for each event:

Edges have a slightly simpler format, with an ID and vertex/event IDs for Source and Target vertices of each directed edge between events. The additional metadata consists of an edge Type, which included things such as "Successful time travel" or "World swap". Finally, certain edges have a Description if some elaboration on the relation between events was necessary. The features of edges can then be described as:

The total graph had $554$ vertices and $628$ edges.

The raw data forming the basis of the dataset was extracted from a Reddit post on r/DarK by user u/aldersonloop59.¹¹1https://www.reddit.com/r/DarK/comments/hqnzgf/spoilers_s3_d_a_r_k_the_complete_visual_timeline/ The Reddit post refers to an interactive Lucidchart, a tool to create diagrams, such as flowcharts and mindmaps. While this Lucidchart document of Dark is very comprehensive, Lucidchart itself is just a visualization tool, and not meant to internally represent complex graph structures with metadata. As such, the XML output generated by Lucidchart could not capture all the relational information and metadata visualized in the document. Hence, the contest committee took on the labor-intensive task of manually extracting all the data into two tables for vertices and edges. In the process some wrong information was corrected and many bits and pieces were refined — using the committee’s knowledge of the Dark plotlines — to create the final dataset.

We received 12 submissions for the creative challenge. Submissions were evaluated according to four criteria:

1. 1.

   readability and clarity of the visualization,

2. 2.

   aesthetic quality,

3. 3.

   novelty of the visualization concept, and

4. 4.

   design quality.

In practice, we asked ourselves the following questions to assess these criteria: (1) How much does this submission help you understand (parts of) the data? (2) Do the aesthetics fit the theme of Dark? (3) Does the submission require (involved) graph drawing techniques? And this year especially: how well is the circular screen utilized? (4) How coherent and polished is the submission? As is the case every year, we noticed that it is a difficult decision to choose one submission over the other, and it takes a lot of discussion to weigh all the criteria against each other and come to a definitive top 3. To ease this discussion and to keep the creative topic managable at the conference, we selected a top six out of all submissions before the conference. This top six was exhibited in the Norrköping Decision Arena during a dedicated session at the Graph Drawing Symposium. We also made all the submissions available on the contest website in the form of a virtual poster exhibition. For a complete list of submissions, refer to https://www.graphdrawing.org/gdcontest/2025/results/.

As always, the live challenge took place during the conference and lasted exactly one hour. During this hour, participants of the conference could take part in the manual category (in which they could attempt to draw the graphs using a supplied tool: http://graphdrawing.org/gdcontest/tool/), or in the automatic category (in which they could use their own software to draw the graphs).

We introduced a new rule this year, allowing teams to participate only if they have a representative attending the conference. This representative can be a team member, or another (closely related) member of the GD community, such as a supervisor (of student team), collaborator, or friend. The contest is organized for the GD community, and hence we think it is important that the participants interact with each other and with the community, to share knowledge about how to efficiently solve the challenges in the contest.

To coordinate the contest, we gave a brief introduction, answered questions, and gave participants the possibility to form teams. We were kindly provided with both a room in the conference building, and laptop facilities, to accommodate to the needs of the participating teams. The largest automatic contest instance gave some teams technical issues, as the server would sometimes have problems storing the solutions sent in by teams. Luckily resending the solutions would resolve this issue, and the contest was otherwise uneventful in terms of technical issues.

The challenge of this year’s contest was to draw a given undirected graph on a given grid, while ensuring that the straight-line drawing was $k$-planar for as small a $k$ as possible. We did not allow for points to lie on (the interior of) edges. For each edge we count the number of crossings, and the edge with the largest number of crossings for a single edge determines the quality metric $k$ of a drawing. The study of $k$-planarity and $k$-planar graphs is an active field of research within graph drawing, and hence this contest topic forms a timely challenge to the community to put the obtained knowledge into practice.

The 2025 edition of the Graph Drawing Contest was another success in both participation and result. While the attendance to the GD conference was a bit lower than in Vienna (2024), the total number of creative topic submissions and participating teams in the live challenge went up. The participation in the live challenge remained strong, even though the committee introduced a new rule that requires each team to have a representative at the conference. This is a good sign, as it shows that there are enough participants in the community, or the participants from outside the community are willing to attend to conference. As such, this new rule achieves exactly the intended outcome: it creates engagement and discourse within the Graph Drawing community and attracts outsiders to participate in our community. The opportunity to use the Decision Arena in Norrköping was also a highlight of his year’s contest. Participants loved seeing the submissions in an entirely new and unusual format, and the committee is really grateful to the organizers for helping us to make this happen. The committee will look out for more such opportunities in the future.