placing circles and arcs on a sphere d3.js

Hello,

I am new to programming d3.js , I want to draw : points, texts and 3D arcs on a sphere like this expemle map http://bl.ocks.org/dwtkns/4973620 , but instead of polygons I would like to use circles on the surface sphere , I did not understand how he used the coordinates of the polygons in the JSON files. https://github.com/mbostock/topojson/blob/master/examples/world-110m.json?short_path=543d9f1
I need your help and if you have a simpler exmples .

cordially.