In an example, a method includes forming, at an additive manufacturing apparatus, a first layer of build material to be processed in the generation of an object. A print agent is selectively applied onto the first layer based on a first print instruction associated with the first layer. Energy is applied to the first layer to cause fusion in a region of the first layer. The method further comprises: measuring the temperature of the first layer at a plurality of locations to form a measured temperature distribution profile; comparing the measured temperature distribution profile against a predicted temperature distribution profile to generate a difference; and correcting a temperature distribution profile of a subsequent layer of the build material following fusion of the subsequent layer based on the difference by modifying a second print instruction associated with the subsequent layer.