Algorithm:

The following summarizes the algorithm:

Input : A set of m + 1 rows and n + 1 columns of control points, knot vectors in the u- & v-directions and (u ,v);

Output : Point on the surface p(u, v)

Algorithm

Consider u be in [u_c, u_{c + 1});

Consider v be in [v_d, v_{d + 1});

If u is not equal to u_c, assume s be zero; otherwise, Consider s be the multiplicity of u_c;

If v is not equal to v_d, consider t be zero; or else, Assume t be the multiplicity of v_d;

for i = c - p to c - s do

     begin

By Appling de Boor's algorithm to control points p_{i, d - q,} p_{i, d - q+ 1,} . . . , p_{i, d - t} with respect to v;

Let the result be q_i (v);

end

By apply de Boor's algorithm to points q_{c - p} (v), q_{c - p + 1} (v), . . . , q_{c - s} (v) with respect to u;

The point attained is p (u, v);