No, the functions which test the straight-line distance between a given line endpoint and the two polyline segment endpoints will also perform correctly with 3D points (providing all three points are expressed relative to the same coordinate system, which they are in my example).
Yes, that is true. My thought was more of , if in a plan view, were the line were directly under the segment, but not on the same z axis. A 2D only kind of test.
-David
Oh I see - a sort of 'apparent collinearity', view-dependent.
