Abstract: Aspects of the disclosed technology relate to techniques for applying optical proximity correction to free form shapes. Each optical proximity correction iteration comprises: computing edge adjustment values for the straight ty correction iteration immediately preceding the each of the plurality of optical proximity correction iterations, adjusting locations of the straight line fragments based on the determined edge adjustment values, determining smooth boundary lines for the layout features based on the straight line fragments on the adjusted locations, performing a simulation process on the layout features having the smooth boundary lines to determine a simulated image of the layout features, and deriving the edge adjustment errors for the straight line fragments based on comparing the simulated image with a target image of the layout features.