Generating control data for sub-objects

Apparatus to generate control data for production of a three-dimensional object comprising:

• an interface to receive data representing a model of the three-dimensional object as an array of voxels;
• a classifying module to classify the voxels as comprising part of a first or a second sub-object of the three-dimensional object;
• a mapping module to map each first sub-object voxel to a volume coverage representation defining print material data at each first sub-object voxel, and to map the second sub-object voxels to a volume coverage representation defining common print material data for the second sub-object voxels as a whole;
• a halftoning module to halftone the first sub-object volume coverage representation to generate control data for printing the first sub-object;
• and
• a control data assigning module to generate control data for the second sub-object according to the volume coverage representation of the second sub-object, the control data assigning module comprises:
• a volume generator to determine dimensions of a cuboid enclosing the second sub-object;
• a random point generator to generate a set of random points dispersed over the cuboid, wherein a number of generated points is determined using the volume coverage representation of the second sub-object and a resolution of an apparatus to generate the object;
• and
• a control data module to determine, for each point, whether that point is contained within the second sub-object and, if so, determining control data indicating that print material will be deposited at that point.

A non-transitory computer readable storage medium encoded with instructions, executable by a processor, comprising:

• instructions to classify voxels of a representation of a three-dimensional object as representing a first or a second sub-object based on a desired level of detail;
• instructions to map each first sub-object voxel to a volume coverage representation defining an amount of print material at that voxel on a voxel-by-voxel basis;
• instructions to map the second sub-object voxels as a whole to a volume coverage representation defining an amount of common print material for the voxels of the second sub-object;
• instructions to generate control data for generating the first sub-object, the control data being generated from the volume coverage representation of the first sub-object;
• and
• instructions to generate control data for generating the second sub-object according to the volume coverage representation of the second sub-object by:
• determining the dimensions of a cuboid enclosing the second sub-object;
• generating a set of random points dispersed over the cuboid, wherein a number of generated points is determined using the volume coverage representation of the second sub-object and the resolution of an apparatus to generate the object;
• and
• determining, for each point, whether that point is contained within the second sub-object and, if so, determining control data indicating that print material will be deposited at that point.