Efficient maths algorithm to calculate intersections

Question

For a game I am developing I need an algorithm that can calculate intersections. I have solved the problem, but the way I have done it is really nasty and I am hoping someon

Answer 1

A simple optimization that may save you alot of time is to check the axis-aligned bounding boxes of the lines prior to getting into the intersection calculation.
If the bounding boxes are completely disjoint then you can be certain there is no intersection.
Of course this is dependent of the data you have. if an intersection is very likely in every check you make then you might find yourself wasting time on a check that is always true.