1. A method for selectively transforming a multi-dimensional input array comprising D dimensions, said method comprising: with a computing system, determining a D-dimensional convolution of said input array at only selected points in said array, each said convolution being a function of a product of D one-dimensional kernels; with a computing system, determining partial convolutions at each dimension iteratively, an iterative determination of one of said partial convolutions being determined, in part, from a previous iterative determination; and with a computing system, collecting transformed values from said convolutions into said input array to form a transformed input array.