@roelvdwal that is a sort-of solution. You would need to have a virtual boundary for each source, like a 3-dimensional box that it can't leave, and whenever a player comes close it needs to follow them along the edges, and stay literally on top of them when they are inside the defined cube.
The problem with this (at least as I see it) is that this means a lot of custom code. This was one of the ideas I had when trying to think up something that would accomplish what the original poster mentioned.
Though I could do it, and it might (might) add up to what I wanted, it would be more work than I felt like doing.
I don't have a problem with writing a lot of code to do exactly what I want, but I *hate* duplicating code, and if I wrote a solution (even a partial one) for this, it has less of a chance of being implemented in the library itself. Also it's guaranteed to run slower than something written in c++ would.
For now I've updated my game's map editor to allow for size specification of sources. it's not perfect and I can't clearly define boundaries like I want to, but I have larger things to code, and this problem might just solve itself eventually.
Regards,
Blademan
Twitter: @bladehunter2213