A method and apparatus for designing a lithography mask set which provides polygon features of a desired size at advanced technology nodes, for example, using live features and dummy features. A dummy feature can be formed within a confined space by specifying an allowable dummy feature length even though the feature length may result in contact between the dummy feature and the live feature. After specifying the dummy feature length, a pattern generation (PG) extract can be performed to pull back the dummy feature away from the live feature by an allowable distance. The PG exact process can result in a shorter dummy feature which has a length which is shorter than can be specified directly by design rules, but which passes rule checking.