Let a space curve have line elements d s_N, d s_T, and d s_B along the normal, tangent, and binormal vectors respectively, then d s_N^2 = d s_T^2 + d s_B^2, where d s_N^2 | = | (κ^2 + τ^2) d s^2 d s_T^2 | = | κ^2 d s^2 d s_B^2 | = | τ^2 d s^2, and κ and τ are the curvature and torsion, respectively.

curvature | torsion | total curvature