1. A method of generating a model for simulating the imaging performance of an optical imaging system; said method comprising the steps of: defining said optical imaging system and a process to be utilized by said optical imaging system; defining a first model representing the imaging performance of said optical imaging system and said process and calibrating said model, said first model generating values corresponding to a developed image dimension and a latent image slope; and defining a second model for estimating a line width roughness of a feature to be imaged, said second model utilizing said latent image slope values to estimate said line width roughness.