Returns the vertical coordinate of a taxi flight's source node. Used in the default UI to draw lines between nodes;
TaxiNodeSetCurrent() should be called first so the client can compute routes.
See also Taxi/Flight functions.
source- Index of the source flight point (between 1 and
dest- Index of the destination flight point (between 1 and
sY- Y coordinate of the source taxi node (as a proportion of the taxi map's height; 0 = bottom, 1 = top) (