A removable build module to connect to a host apparatus, may include a build platform to support an object-to-be-built, a drive unit to move the build platform, a memory to receive and store build parameters, and an interface circuit to communicate the build parameters to the host apparatus.

A removable build module to connect to a host apparatus, may include a build platform to support an object-to-be-built, a drive unit to move the build platform, a memory to receive and store build parameters, and an interface circuit to communicate the build parameters to the host apparatus.

A method of calibrating an apparatus for generating a three-dimensional object is described in which a calibration substrate is generated by depositing build material and applying energy to the build material to form a fused surface; a calibration pattern is generated on the calibration substrate by depositing an agent on the calibration surface according to a predetermined pattern; and an attribute of the calibration pattern is measured.

A method of calibrating an apparatus for generating a three-dimensional object is described in which a calibration substrate is generated by depositing build material and applying energy to the build material to form a fused surface; a calibration pattern is generated on the calibration substrate by depositing an agent on the calibration surface according to a predetermined pattern; and an attribute of the calibration pattern is measured.

A method for processing an object for printing, the object comprising a plurality of properties defined at each of a plurality of locations within the object, each property represented by a metamer set of possible combinations of proportions of at least one of a set of printing materials, the method comprising: selecting a combination of the metamer sets of a given location within an object that provides all of the plurality of properties defined for the given location.

A method for processing an object for printing, the object comprising a plurality of properties defined at each of a plurality of locations within the object, each property represented by a metamer set of possible combinations of proportions of at least one of a set of printing materials, the method comprising: selecting a combination of the metamer sets of a given location within an object that provides all of the plurality of properties defined for the given location.

Methods and apparatus associated with three-dimensional objects are described. In an example, a method comprises receiving data representing a three-dimensional model object, the data comprising object model data and object property data. For at least one object property, a sub-region of the object in which the object property is non-variable is identified and, for at least one location within the object, all sub-regions in which the location is situated are identified. Based on the combination of identified sub-regions for a location, print material data is determined for the location. Control data for the production of a three-dimensional object is generated according to the print material data.

Methods and apparatus associated with three-dimensional objects are described. In an example, a method comprises receiving data representing a three-dimensional model object, the data comprising object model data and object property data. For at least one object property, a sub-region of the object in which the object property is non-variable is identified and, for at least one location within the object, all sub-regions in which the location is situated are identified. Based on the combination of identified sub-regions for a location, print material data is determined for the location. Control data for the production of a three-dimensional object is generated according to the print material data.

Methods and apparatus relating to substructures for 3D objects are described. In an example, a method for providing a three-dimensional halftone threshold matrix is described. The method may comprise receiving a substructure model representing a three-dimensional material structure and populating each location in the substructure model at which the structure exists with a halftone threshold value.

Methods and apparatus relating to substructures for 3D objects are described. In an example, a method for providing a three-dimensional halftone threshold matrix is described. The method may comprise receiving a substructure model representing a three-dimensional material structure and populating each location in the substructure model at which the structure exists with a halftone threshold value.