Fig. 16.

Diagonal refinement of the unit square, starting from a uniform $4\times 4$ mesh, after six refinement steps: $\mathcal{H}$-admissible (left) and $\mathcal{T}$-admissible (right) meshes generated by Algorithm 1 and 2, respectively. Results for $\mu =3$ and $\mathbf{p}=(2,2)$, $\mathbf{p}=(3,3)$, $\mathbf{p}=(4,4)$. At each refinement step, we mark a strip of $2\lceil \frac{p+1}{2}\rceil$ cells centered at the diagonal. This naturally guarantees that in each step functions of the finest level are activated. All internal knots have multiplicity one