Fig. 3.

Isogeometric elements $b_i({\mathbf{x}}_{\alpha })≔N_{\alpha ,i}◦{\mathbf{x}}_{\alpha }^{-1}$ on the unit disk. The unit disk is partitioned into patches x_α whose boundaries run dual to the input DS-mesh (cf. Fig. 2b). The support of the irregular b_i is that of bi-2 B-splines taking into account that some facets are n-gons. (a) shows the xy-coordinates of DS-mesh control points of the irregular isogeometric elements (b–e) as well as a regular boundary element (f).