Thursday, May 8, 2008

Viewing missing methods/software, part V: Processing

In my previous post, I was  bemoaning the slow speed of the visualization chart using Google Maps. Looking around in the Google Maps group, it seemed that there wasn't a good way to speed up the drawing of many markers, except for drawing them in another program first and storing them on image tiles. Since I was going to have to draw markers in a different program anyway, I decided to try using such a program by itself without involving Google Maps. First, I thought to create a static image using GD with PHP and then do an image map on top of that with javascript, but GD wasn't working on the NESCent server (this was fixed in just a couple of hours, as is common with NESCent's great tech support). While it was being fixed, I decided to learn Processing — I've been impressed by the quality of some of the diagrams it creates, and having a dynamic diagram might be more useful for users. It has good documentation and can parse XML, so within a few hours, I learned enough to be able to create the diagram below. 

Following advice from the TreeTapper design consultant (my wife), I made the nodes smaller and changed the color slightly, but otherwise it is the same as the Google diagram (though I don't have popups or mouseovers working yet), and is much faster to create. It does require users to have Java installed in their browsers, but might allow cool features later on.

Viewing missing methods/software, part IV: Sort of working

Well, I sort of have the visualization working. Users can choose which elements to graph (on Firefox) by dragging boxes to move them above or below a plotting line, and they can choose to limit to plotting only one of many options. See below.

On clicking the  update chart button, a tree is plotted using the Google Maps API, with branches colored based on whether they have no methods or software, methods but not software, or both methods and software [I originally had it update the map automatically on any change, but this is too slow]. Users can click on nodes to get an info window showing the choices made going from the tree root to the tips and links to any relevant software or methods. Just mousing over a node tells a user what option that node represents (i.e., "Treetype: Unrooted, polytomies, incomplete tree"). If a user has chosen just one setting for an option (as for criterion, below), the edge leading to that node is shorter and light gray edges are shown to indicate the options not examined.  See below (click to make larger).

The end product is beautiful and information-rich. It's also VERY slow. It takes literally minutes to generate the plot, and then >10 seconds between clicking on a node and getting the info window. Zooming in or out or moving the plot also take an agonizingly slow time. Getting info from the script that talks to the database to make code for the map takes a while, about 30 seconds, but the real slowdown comes when drawing the map. Google maps are slow with many markers and polylines: the map above has 221 markers and even more polylines, with the three circle polylines having 360 points each (using fewer makes a plot that's too rough). I'll have to decide what to do. I'd stayed away from Processing due to usability concerns, but it seems Google Maps isn't so great, either. I've read a little about generating image tiles rather than markers to speed up the map -- I'll look into this and other options.