1. A method implemented by a computer comprising: identifying a model of a lithographic process; using, by the computer, the model to generate a function that simulates an image produced by the lithographic process, the function having one or more variables representing process window variations from a nominal process condition associated with the lithographic process; generating, using the computer, a plurality of simulated images utilizing the generated function, the plurality of simulated images respectively corresponding to a plurality of different lithographic process conditions that are variations from the nominal process condition; and analyzing the plurality of simulated images to determine a process window associated with the lithographic process.