Intersecting Line Segments

[NotLKH]

I'm down to the final step of a progie of mine, just have to build an intersection test.


Whats the best way to determine if 2 line segments intersect.

I figure, given 2 line segments, 1-2, 3-4:

1. Test for parallelity, return False if parallel.
2. If Not parallel, calc intersection points of the 2 lines. (Call it 5)
3. Return False if one or more of the following distance comparisons are true:
   
   
   • 5 to 1 > 1 to 2
   • 5 to 2 > 1 to 2
   • 5 to 3 > 3 to 4
   • 5 to 4 > 3 to 4
4. Else return True.

Is there a more optimal strategy?