How are they made?

Let’s explain exactly how they are calculated and what they are showing, to do this lets looks a little more closely at one of my favourite corals — Tokyo.

Tokyo City — 30 minute catchment

I start with a basic OpenStreetMap network for the city of Tokyo and the surrounding region. Using various methods I can then calculate the catchment area for a designated drive-time from the centre. At Ito World (www.itoworld.com) we have an in-house routing system which allow us to do this, however, there are a bunch of other methods and software which allow you to calculate drive-times (ESRI, PgRouting, GraphHopper, Here API etc). It’s important to note that in most cases the network catchment is calculated with zero traffic so the results are very optimistic. However, we have experimented with importing congestion based isochrones from the Here API and converting these to corals which has been fairly successful (see below)

Comparing congestion catchments in the worst/best cities using data from Here API.

The catchment analysis will give a rough area, I then need to turn it into Corals, to do this each vertex on a linear link is given a distance value away from the centre of the city. I can use this distance metric as a height value for the link, creating a 3d network, growing higher with distance from the centre.

I also apply a ‘weight’ value to the link, this isn’t anything to do with the road classification, however it is often linked. The weight is proportional to the number of links connected to the branch, so the thicker networks have more arterial networks connected creating a coral-like appearance, it also suggests busier sections of the routing network.

Each of the links then undergoes a ‘sweep’ with a rectangular geometry creating a physical presence with which we can apply ambient occlusion to during our render.

The colour gradient is purely an aesthetic addition and just maps the gradient from the centre. Animating the links to appear in order of distance results in a mesmerising coral growth…

UK Cities — Coral Animation

Bespoke Versions

My wife usually takes very little interest in my work :) however she was quite taken with the Coral City posters, so much so that she commissioned me (payment in endless cups of tea and coffee!) to produce one for the house. Being a big history geek the topic was ‘Historically Important Coral Cities.’ We are still figuring out framing options but below are a couple of screenshots of the poster.

Cinema4d/Blender Renders:

Throughout this process, I have been increasingly interested in the possibilities of porting the analysis from our visualisation suite at Ito World into other 3d packages such as Cinema4d. This has been tricky… our analysis tools analyse each link of a network, node to node links are split with a height value for each node. This value then gets put into a shader with a z-min and z-max attribute which creates the height of the link. A similar method is also used for the links thickness. So importing this into other packages isn’t simple and results in massive amounts of CSV files. I did develop a methodology for Cinema4D but the process is pretty time-consuming but does result in some lovely looking renders.