Function vector

A line is stored as an array [0, c, a, b, 0, 0, 0, 0] representing: c * e0 + a * e1 + b*e2

This maps to a standard formula a * x + b * y + c.

(-b, a) corresponds to a 2D vector parallel to the line. The lines have a natural orientation, corresponding to that vector.

The magnitude ("norm") of the line is sqrt(a ^ 2 + b ^ 2). c / norm(line) is the oriented distance from line to origin.