code: function(traces, vertsPerSlice, splineDetail) {
    var numVerts = 0;
    for (var i = 0; i < traces.length; ++i) {
      var traceVerts = 
        ((traces[i].length() - 1) * splineDetail + 1) * vertsPerSlice;
      // in case there are more than 2^16 vertices for a single trace, we
      // need to manually split the trace in two and duplicate one of the
      // trace slices. Let's make room for some additional space...
      var splits = Math.ceil((traceVerts + 2)/65536);
      numVerts += traceVerts + (splits - 1) * vertsPerSlice;
      // triangles for capping the tube
      numVerts += 2;
    }
    return numVerts;
  }
docs: calculates the number of vertices required for the cartoon and tube render styles