Multilevel Agglomerative Edge Bundling in JavaScript

This is a JavaScript implementation of the paper Multilevel Agglomerative Edge Bundling for Visualizing Large Graphs (Emden R. Gansner, Yifan Hu, Stephen North, Carlos Scheidegger).

The edge bundling algorithm groups edges together to minimize the amount of ink used to render a graph. This particular paper introduces a fast technique to perform edge bundling.

Take for example this map connecting locations between the east coast in the US and western Europe:

The algorithm creates a proximity graph for the edges where each of the edges is represented by a node. Then the algorithm bundles edges as long as we're saving some ink in the final rendering. Here's an intermediate step on the bundling animation:

And here's the final result:

This implementation is solely based on the paper. The license for the code is MIT.

Examples

This simple example shows links connecting locations in the Bay Area. The rendering uses 2D Canvas but could use any other rendering API.

You can see an example here.

Usage

Given a dataset consisting of an Array of elements with format:

  {
      "id": <string id>,
      "name": <string name>,
      "data": {
          "coords": [
              <coord x from>,
              <coord y from>,
              <coord x to>,
              <coord y to>
          ]
      }
  }

Then the code to create the bundled edges graph is:

  var bundle = new Bundler();
  bundle.setNodes(json);
  bundle.buildNearestNeighborGraph();
  bundle.MINGLE();

Finally, to render the graph we provide some helper functions that make use of 2D canvas:

  bundle.graph.each(function(node) {
    ctx.strokeStyle = 'rgba(0, 200, 200, 0.2)';
    ctx.lineWidth = 2;
    var edges = node.unbundleEdges(delta);
    Bundler.Graph.renderBezier(ctx, edges);
  });

External libraries used

• kdtree implementation by Ubilabs can be found here. MIT license.
• PhiloGL is used to perform animations between unbundled and bundled edges. This library is not required to use the algorithm. MIT license.

TODO

Provide a more complete documentation and API reference.

Copyright Twitter, Inc.

The code is copyright Twitter, Inc. with an MIT license.

    Copyright (c) 2013 Twitter - Author: Nicolas Garcia Belmonte
    (http://philogb.github.io/)

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