I spent a weekend trying to figure out the flight-path mechanics, and while I did come pretty close to accurately modeling them, I'm stumped by a few issues. Since I doubt I'll make anymore progress without a big time commitment, here's what I've found so far:
- WoW smooths the paths between TaxiPathNode points using splines—specifically, Catmull-Rom splines. I wrote a test addon so I could experimentally compare expected and measured flightpaths, and Catmull-Rom seems 100% accurate.
Cyan line is the expected path, red line is the measured path, alternating yellow and purple sets of dots mark joined path splines' control points, yellow gridlines are map chunk boundaries, and the red crosshair centers on the player.
- For multi-part flights, WoW takes the shortest combination of paths, unless a direct route is available. The "length" of a path is the length of the Catmull-Rom spline in 3D space, found through integration.
- Where two paths join together, WoW seems to dynamically strip away spline control points between them that would make too sharp a turn. I didn't attempt to reverse engineer the algorithm, since it would just be a bunch of guesswork and tweaking without WoW's source code available. My test addon defines a function GetSkippedNodes in case anyone wants to attempt to implement this properly. For now, it returns placeholder values 1,1 to skip one innermost point from each joined path. Here are a few examples where paths join incorrectly:
While I was taking screenshots for this post, I noticed that last example where WoW actually makes a tight turn. Who knows.
- I couldn't find any way to estimate flight-path speeds. It's definitely not constant across all paths, and instead seems to be determined by the node you depart from. The NPC ID of your flight-path mount (from TaxiNodes) works the same way, but I don't know if your mount affects your speed here. Even if it does, I couldn't find a lookup for NPC speed in my cache files or the DBCs.
I have noticed that flight-path speed appears to vary, but GetUnitSpeed doesn't reflect it. I assume any visual speed change is just rubber-banding when you periodically synchronize your flight-path progress with the server.
Overall it's still pretty inaccurate because of lag, unknown speed, and the path joint issue. Oh well, it was still a fun project.
My test mod is attached if anyone wants to play with it. "
/taxi" opens the grid, and you can navigate around sort of like Google Maps. If you talk with a flight master while the grid is open, hovering over nodes will plot their expected paths.