Sub-volume octrees

A machine readable medium comprising instructions which, when executed by a processor, cause the processor to:

• generate, from object model data, a plurality of first data models and a second data model representing an object for generation in layer-by-layer manufacturing by inspecting groups of eight volumes of a first size, and, for each group:
• if the group consists of volumes which share a predetermined attribute, merging the volumes to define a volume of a second size which has the predetermined attribute;
• otherwise, if the group consists of volumes which lack the predetermined attribute, merging the volumes to define a volume of the second size which lacks the predetermined attribute;
• otherwise, defining a node, wherein the node is indicative of a volume of the second size which comprises the attribute in a sub-portion thereof;
• wherein the instructions to define nodes and/or volumes in generating the first data models are instructions to define nodes and/or volumes iteratively based on inspecting nodes and/or volumes defined in a preceding iteration until a volume of the second size reaches a predetermined size, wherein a node indicative of the volume of the predetermined size is defined;
• and
• wherein the instructions to define nodes and/or volumes in generating the second data model comprise instruction to, starting from the nodes of the predetermined size defined in generating the first data models, define of nodes and/or volumes iteratively based on inspecting nodes and/or volumes defined in a preceding iteration until a single node is indicative of a volume containing the object;
• and
• the instructions further comprise instructions to cause the processor to store the plurality of first data models.

A machine readable medium comprising a representation of at least part of an object to be manufactured in a layer-by-layer manufacturing process, wherein the representation comprises:

• data representing an octree having first plurality of nodes spanning volumetric resolutions of the object between a first resolution and a second resolution;
• and data representing each of a plurality of octrees having second plurality of nodes spanning volumetric resolutions of the object between a third resolution and a fourth resolution;
• wherein, in each octree, nodes are ordered such that
• (i) a node representing a volume which includes a layer of the object to be generated earlier in an intended order of object generation precedes a node representing a volume which consists of layer(s) of the object to be generated subsequently;
• (ii) for nodes representing a volume which includes a given layer of the object, nodes at a coarser volumetric resolution precede nodes at a finer volumetric resolution;
• and
• (iii) nodes representing a volume which includes a given layer and being of the same resolution are ordered according to a predetermined location encoding pattern.