Exponential basis

See [Delgado2012].

(1)\[\begin{split}\phi(t)=\begin{cases} \frac{\cos\frac{2\pi|t|}{M}\cos\frac{\pi}{M}-\cos\frac{2\pi}{M}}{1-\cos\frac{2\pi}{M}}, & |t| \in [0,\frac{1}{2}[\\ \frac{1-\cos\frac{2\pi\left(\frac{3}{2}-|t|\right)}{M}}{2\left(1-\cos\frac{2\pi}{M}\right)}, & |t| \in [\frac{1}{2}, \frac{3}{2}[\\ 0, & \mathrm{elsewhere} \end{cases}\end{split}\]

where \(M\) is the number of control points.