# Fundamental theorem of curves

A curve can be described, and thereby defined, by a pair of scalar fields: curvature $\kappa$ and torsion $\tau$, both of which depend on some parameter which parametrizes the curve but which can ideally be the arc length of the curve. From just the curvature and torsion, the vector fields for the tangent, normal, and binormal vectors can be derived using the Frenet-Serret formulas. Then, integration of the tangent field (done numerically, if not analytically) yields the curve.