A three-dimensional object may be generated. A temperature sensor may be to measure a temperature distribution of build material delivered to a support member. A processor may be to mask a masking region of the measured temperature distribution or correct the measured temperature distribution, based on emissivity data of the build material. A heater may be to heat the build material to a target temperature distribution based on the corrected or masked measured temperature distribution. An energy source may be to apply energy to the build material to cause a portion of the build material to coalesce.