1. A system configured to generate simulated output for a specimen, comprising: one or more computer subsystems configured for acquiring information for a specimen, wherein the information comprises at least one of an actual optical image of the specimen, an actual electron beam image of the specimen, and design data for the specimen; and one or more components executed by the one or more computer subsystems, wherein the one or more components comprise a learning based model, wherein the learning based model is configured for mapping a triangular relationship between optical images, electron beam images, and design data, wherein the one or more computer subsystems are configured to input the information for the specimen into the learning based model, and wherein the learning based model applies the triangular relationship to the input to thereby generate simulated output for the specimen.