Abstract: Disclosed are techniques for processing layout designs based on dynamically-generated lithographic models. Lithographic models are determined for a plurality of regions of a reticle prior to lithographic simulation. During lithographic simulation, lithographic models for a small area within a particular region are generated based on the lithographic models for the particular region, the lithographic models for one or more neighboring regions, and location information of the small area relative to the region and to the one or more neighboring regions. The lithography models comprise illuminating and imaging system models and mask electro-magnetic field models.