A method for generating or refining an OPC model for use in wafer fabrication. A predetermined feature layout is used to prepare a mask for use in, for example, a photolithographic process. The mask is used to create structures corresponding to mask features on a semiconductor wafer using the mask. Measurements of the actual mask features and wafer features may then be assessed and correlated, and the results used to generate an OPC model or refine an existing one. In addition, the OPC may be used to simulate a fabrication operation by applying the OPC tool to a predetermined layout to produce a mask image and a wafer image, and then comparing the predetermined layout to the simulated wafer image to determine at least one fitness value.