In an example, a method includes obtaining a plurality of models each representing an object to be generated in an additive manufacturing operation. In some examples the method further includes identifying a set of models of the plurality of models which represent instances of similar objects. The method may include determining whether the objects represented by the models of the set of models are to be generated relatively rotated with respect to one another. In some examples the method further includes, when the objects represented by the set of models are to be generated relatively rotated with respect to one another, providing an indication of the relative rotation.