1. A method of verifying a lithographic mask, the method comprising the steps of: providing a mask layout; providing a catastrophic error metric; providing a plurality of image models, wherein said plurality of image models comprises a plurality of kernels ranked according to decreasing image contribution; simulating an image for said mask layout using at least one of said plurality of image models comprising a first subset of said plurality of kernels; identifying a violation of said catastrophic error metric in said simulated image; identifying a portion of said mask layout corresponding to said simulated image that includes said violation; and simulating a next image for said portion of said mask layout using a next of said plurality of image models comprising a second subset of said plurality of kernels comprising said first subset of said plurality of kernels and at least an additional one of said plurality of kernels having less image contribution than said kernels of said first subset.