This method sets the edgeMode which is one of "straight" or "curved".
The example on left has the default edgeMode="curved" and the example on the right has edgeMode="straight".
For other options and examples, check VizJS
Modified http://vizjs.org/viz.v1.1.0.min.js to a secure url
https://d3js.org/d3.v4.min.js
https://vizjs.org/viz.v1.1.0.min.js