Abstract: The invention provides a method for spatially refining a computer generated l-dimensional (l>0) model in a computing environment, the l-dimensional model representing physical or geometrical properties, and where the l-dimensional model is represented by tensor product B-splines basis functions and l-dimensional coefficients, where the l-dimensional coefficients are in real or projective space, and the tensor product B-splines basis functions are spanning an r-variate spline space (r>0) having a parameter domain, the method comprising: a) inserting at least one axis parallel hyper rectangle degenerate in one dimension in said parameter domain, providing a splitting of a support of at least one of said tensor product B-spline basis functions; b) computing refined tensor product B-spline basis functions by subdivision on said at least one tensor product B-splines basis functions whose support is split, using at least one knot value of the at least one axis parallel hyper rectangle; and c) computing the re