Given n points in a 2-D plane,what is the most efficient way to find total number of distinct lines formed by joining all the points with each other??

I know that we can pair-wise take all the points and use hash map to denote the line they belong to and thus count no. of distinct lines,but is there any more efficient way to do this?? And how to do the same thing if points are given in 3-D plane and what's the complexity of this algorithm?