Cover stories: Visualizing scientist migrations

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Science  19 May 2017:
Vol. 356, Issue 6339, eaan6494
DOI: 10.1126/science.aan6494

Cover stories offer a look at the process behind the art on the cover: who made it, how it got made, and why.

The 19 May cover illustrates the journeys of the 20 most migratory scientists in the ORCID database (Fig. 1) [see the related News story in this issue]. To make it clear that the lines represent many individuals, we chose to highlight the one who may be the most migratory living scientist. Contributing Correspondent John Bohannon and Interactive Graphics Editor Jia You analyzed the data to be visualized. I then used a Python script to create the cover in Cinema 4D, my 3D modeling software.

Fig. 1 The 19 May 2017 cover.

The original data set contained the latitude and longitude of each scientist’s migrations. Jia converted these to Cartesian coordinates and provided me with the data in this form. However, if done manually, drawing hundreds of lines between points would be a painstaking, if not impossible, task. Instead, I needed to write a script to tell Cinema 4D how to accomplish this programmatically. Although much thought went into developing the final visual aesthetic, the majority of the effort was spent designing and writing the program.

Essentially, the script reads the position coordinates of the origin and destination of each migration and the associated ORCID for each scientist’s paths. The script instructs Cinema 4D to denote each country with a small sphere and then to draw a line connecting the pairs of origins and destinations.

Drawing these lines presented a 3D math problem to solve, as there is no magic button or built-in function that enables a line to arc around a sphere. I thus had to convert the points to spherical polar coordinates and redirect the midpoint of each line to a position outside of the globe (i.e., the sphere), following a vector pointing outward from the globe’s center. I could then vary the distance of that position, depending on the proximity of any two countries. This resulted in arcs that were appropriately sized (Fig. 2). Many scientists migrated only a short distance, so the arc heights were varied on a square root scale to highlight these minor differences.

Fig. 2 Making arcs.

(Left) Simply sending instructions to draw a line between each pair of points resulted in all of the lines residing inside the sphere representing the globe. (Middle) Setting the midpoint of the arcs to uniformly jut out of the globe gave rise to strangely long lines connecting close-together points. (Right) Result after varying the arc height based on the distance between the connected points.

Once the arcs were sized correctly, the rest came down to Cinema 4D’s native functionality. I wrapped a world map around the sphere and situated the viewpoint to adequately showcase the highlighted path. A shallow depth of field and simple coloring scheme helps the viewer focus on the highlighted scientist’s moves and the popular hub that is Europe.

Valerie Altounian, Senior Scientific Illustrator at Science

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