Testing whether a line segment intersects a sphere

Question

I am trying to determine whether a line segment (i.e. between two points) intersects a sphere. I am not interested in the position of the intersection, just whether or not t

Answer 1

This page has an exact solution for this problem. Essentially, you are substituting the equation for the line into the equation for the sphere, then computes the discriminant of the resulting quadratic. The values of the discriminant indicate intersection.