Intersection of line with cube and knowing the point of intersection

description

1. lines are originating from origin(0,0,0).
2. lines are at some random angle to the Normal of Top face of the cube.
3. if the li开发者_如何学编程nes are intersecting cube, calculate the intersection point.
4. mainly I want to know how much distance the line traveled inside the cube.

I don't know exactly which approach I should take, I would be pleased and thankful if someone could guide me to the right direction, to use OpenGL, DirectX or some other library, for C#. Some example or sample will be appreciated.