gistfile1.js

var Network = module.exports = View.extend({

  // ...

  /**
   * Initialize the edge index.
   */
  _initEdges: function() {

    this.edgeIndex = new rbush();
    this.edgeIndex.load(this.data.edgeIndex);

    // Where `edgeIndex` is an array of:
    // [x1, y1, x2, y2, {metadata}]

  },

  /**
   * Clear the current background edges and render a new set of edges that
   * fall within the current viewport. Called after the scene is panned.
   */
  filterEdgesByExtent: function() {

    // Query for visible edges.
    var edges = this.edgeIndex.search(
      this._getBoundingBox()
    );

    // Sort by edge weight.
    var edges = _.sortBy(edges, function(e) {
      return 1-e[4].weight
    });

    // Take the X heaviest edges.
    var edges = _.first(edges, this.options.edgeCount);

    // Clear current edges.
    this.edgeGroup
      .selectAll('line.background')
      .remove();

    _.each(edges, _.bind(function(e) {

      // Render the new edges.
      this.edgeGroup.append('line')
        .classed({ background: true })
        .datum({
          x1: e[0],
          y1: e[1],
          x2: e[2],
          y2: e[3]
        });

    }, this));

  }

});