1. A method for generating an aerial image, the method comprising: receiving a mask; generating a matrix of node values based on the mask, wherein each node value corresponds to a node of a plurality of nodes in a lattice; performing a one-dimensional (1-D) approximation of a plurality of first approximation values at corresponding first approximation points between pairs of nodes of the plurality of nodes; and performing a two-dimensional (2-D) approximation of second approximation values at corresponding second approximation points between pairs of first approximation points, wherein Chebyshev polynomials are used to approximate the first approximation values and the second approximation values.