title: Visualizing a DAG
body: <p>I have a large directed acyclic graph that I would like to visualize in a bitmap image.</p>
  
  <p>Ideally I'd like to have all the root nodes at the top of the image, and all of the leaf nodes at the bottom, i.e. the graph edges are all pointing in a downwards direction.</p>
  
  <p>Is there a good algorithm for working out the coordinates of all the nodes that meets these constraints and will produce a good visualization?</p>