1. A computer-implemented method of sampling lithographic content producible by a lithographic printing process, the method performed using at least one computing device, the method comprising: identifying parameters for a model of the lithographic printing process; assembling a population of design content including potentially printable features that can be printed by the lithographic printing process; preparing at least one matrix expressing a similarity between the potentially printable features in terms of the parameters for the model, wherein the at least one matrix is formed from similarity weights that express similarity relationships between neighboring features; determining a manifold of smaller dimensionality than the parameters for the model which exhibit maximum variation in similarity within the at least one matrix, using the at least one computing device, wherein the manifold of smaller dimensionality is determined from low-dimensioned coordinate assignments for the potentially printable features that reproduce similarity relationships between neighboring features within a low-dimensioned space; and selecting a sample dataset of the potentially printable features from the manifold.