Certain examples described herein relate to structure forming for the production of a three-dimensional object. In these examples, different structure forming components or functions are applied to volumes of a three-dimensional object. These structure forming components or functions are arranged to differentially generate a halftone output. The halftone output is generated by processing a material volume coverage representation for the three-dimensional object. The halftone output is used to provide control data for instructing production of a three-dimensional object.