I was looking at the asteroid 131 Vala, the origin of the programming language's name, on the JPL Small Object Database when I heard the sad news of David Bowie's passing. Like many of my age, I grew up not knowing of a world without space travel, the threat of nuclear war or the Thin White Duke. No other artist captured that sense of both wonder and fear of a species walking a tight rope towards its destiny. Would we stumble and fall into oblivion or would we make it to the stars? Were all our heros like Major Tom? Brittle and flawed yet compellingly corageous.
I was thinking these things and more while browsing the JPL website and I noticed that the venerable old Orbit Viewer applet was no longer working. I wanted to watch some celestial bodies move that morning to the sounds of David Bowie so I downloaded the applet source and ported it to Vala. For the music, I added a small gstreamer player that loads and plays a midi file from midiworld.com.
Porting Java code to Vala is relatively easy, especially when it is older code and doesn't have too many of the odd little workarounds that have crept into the language over the years. The quickest part was the library of functions for calculating the orbits, as this is pretty much pure math. The trickiest bit was the interface, which I recreated in Glade and the drawing routines for animating the whole thing. I have been working on a port of the Box2D physics engine, so I have already solved most of these problems before. The end result you see above.
It still needs some work before it's complete - only the play button works and there's no way to adjust the viewport yet, but these are fairly trivial to implement. If anyone is interested in the code, I'll post a link to a Github repo - both the physics and animation routines are particularly interesting if you're starting out, even with the lack of comments.
Thanks for watching, and thanks Starman, for all those Golden Years...