A method comprises receiving data representing a 3D object model. The 3D object model is for use in generating a 3D object in a build chamber by forming a plurality of successive layers. Each layer is formed by providing a layer of build material and applying a volume of a binder agent to a plurality of voxel locations of the layer of the build material. The volume of the binder agent to be applied to each voxel location is based on the volume of binder agent to be applied to proximate voxel locations of the 3D object.