A controller may be to receive temperature data representing a temperature distribution of at least part of a current layer of build material that is measured by a temperature sensor. The controller may be to determine one or more weighting factors representing a degree of influence of each of one or more previous layers of the build material beneath the current layer on a property of the current layer. The controller may be to identify one or more regions in the current layer based on the one or more weighting factors and based on how the property is exhibited by each of the one or more regions. The controller may be to cause the current layer to achieve a target temperature if the temperature data in a selected region of the identified one or more regions does not match the target temperature.