Devices and methods are provided that include advantages such as the ability to identify sizes, shapes and locations of frequently unwanted additional features that occur as a result of photolithographic interference. The additional feature information is obtained through use of simulation methods with reduced processing time or solving a system of equations. This allows a user to quickly find information about additional feature printing before the features are printed, and before the reticle is made. In one example, a portion of a region such as a semiconductor lithography pattern is subtracted from consideration in identifying potential optical interactions. In one example, a ring-like region remains and is analyzed.