getneighbour VEX function
Returns the point index of the neighbour of the point.

int getneighbour(int ptnum, int neighbournum, int inputnum)
Returns the point index of the neighbour of the point. The order is undefined, but will be consistent for consistent geometry. Returns 1 if the neighbournum is out of range for that point, or the point is out of range for that input, or the input doesnâ€™t exist.