According to examples, an apparatus may include a processor and a memory on which is stored machine readable instructions that when executed by the processor are to cause the processor to access a reduced resolution three-dimensional (3D) model file of an object to be built in a build bed of a 3D printing system, the reduced resolution 3D model file comprising a reduced resolution file of a first resolution 3D model file of the object. The instructions may also cause the processor to determine a packing arrangement for the object and a plurality of other objects to be built in the build bed through use of the reduced resolution 3D model file and output the determined packing arrangement for the 3D printing system to print the object and the other objects.