1. A method, comprising: receiving layout data for a plurality of calibration layouts, each of the plurality of calibration layouts having a layout topology belonging to a class of layout topologies; deriving density information for the plurality of calibration layouts based on the layout data; receiving printed contour information for the plurality of calibration layouts; deriving contour deviation information for the plurality of calibration layouts based on the printed contour information; and generating a model for predicting printed contour deviations for the class of layout topologies based on the density information and the contour deviation information.