Path following with orientation to it, with a specified "up"

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This isn't an issue per-se, but it would make sense if this feature was 
available.

The best example for what I mean would be Quaternion.LookRotation(). It has 2 
versions, one that only takes a look vector and one that takes a look vector 
and an up vector. That way the object is both aligned to look in the direction 
that you specified while also being tilted on an arbitrary axis.

This could be useful for making objects align to paths on surfaces of varying 
angles. Imagine a spider going from pathing on the ground to pathing on a wall. 
The up vector from the wall would be perpendicular to that of the floor, and 
the character should be rotating on different axes as it changes direction on 
the wall than it would have on the wall.

I hope I was clear enough, this is a tough concept to put into writing alone.

If this is already possible or if I wasn't clear enough please let me know.

Thanks!

Original issue reported on code.google.com by goal2...@gmail.com on 4 Mar 2011 at 10:09

[GoogleCodeExporter]

Also essential for e.g. flying airplanes around.

(I've just removed iTween from a project and thrown it away because it forces 
"up is always positive Y axis" :( )

Original comment by Adam.M.S...@gmail.com on 7 Jul 2012 at 9:45