“…This feature becomes clearly advantageous when the interfaces are moving in a simulation or a physical model requires structured meshes for an interface problem [8][9][10][11]. Since 1998, several types of IFE spaces have been developed, such as 1D linear IFE [12], 2D linear IFE [1,4,13], 3D linear IFE [14], bilinear IFE [2], quadratic IFEs [15], and 1D IFEs of arbitrary order [16]. Error analysis in [3,4,16,17] show that these IFE spaces have the approximation capability similar to that of standard finite element spaces using polynomials of same degree.…”