Tried recreate apple watch's radial chart with d3. Turns out to be surprisingly hard. D3 natively does not support round corner on arcs, not to mention that conical gradient involves lots of hacks as well.
Used a modified version of d3 by mbostock, which implemented a round corner for arcs in d3, see more details on this pull request on github (which have never made into production):
This pen is using the force layout that comes with the d3 library (http://d3js.org/). I am not invoking the lines to link the nodes and instead use the 'weight' variable created by d3 to set the size of each node. It not only runs faster on the browser (around 780 nodes), but also provides a clear view of who might be 'closer' to you.