Issues with 0.21 on Ubuntu

[JoeStrout]

Thanks, you've been very helpful.  I'm a bit stumped as to why the zone shader should work in the simple WebGL test app, but not in the desktop app.  If you're willing, I think I'll take this to email — I may need to send you a desktop build of the minimal test app.  (And if that still doesn't show the problem, then I'm really baffled!)