1. A method for converting a non-bandlimited pattern layout into a band-limited pattern image to facilitate simulating an optical lithography process, the method comprising: using at least one computer for: receiving the non-bandlimited pattern layout which comprises one or more polygons; receiving an anti-aliasing filter (AAF) kernel, wherein the AAF kernel is configured to convert a non-bandlimited pattern into a band-limited pattern; constructing an AAF lookup table for the AAF kernel, wherein the AAF lookup table contains precomputed values for a set of convolution functions which are obtained by convolving a set of basis functions with the AAF kernel; creating a sampled pattern layout by applying a grid map over the pattern layout; and obtaining the band-limited pattern image by using the AAF lookup table to convolve the AAF kernel with each grid location in the sampled pattern layout, which involves: determining if the grid location is associated with one of the polygons; if so, decomposing the associated polygon into a set of flashes, wherein each flash is an instance of one of the set of basis functions; for the grid location, retrieving a corresponding precomputed value in the AAF lookup table for each flash in the set of flashes; and summing together the set of retrieved precomputed values to obtain a convolution value at the grid location; wherein the band-limited pattern image facilitates performing a discrete Fourier transform (DFT) operation on the band-limited pattern image.