I've got an implementation in java of Douglas Demyen Modified Funnel Algorithm pseudo code in my game but for some unknown reason, sometimes the path goes outside the channel.
Looks like I need to Google my name more often. Are you still having this issue? The attachments aren't showing up at the moment and I haven't looked at the code in a while but I can offer some input if you need. As a shot in the dark, is the channel wide enough?
