Autobox is Minetest Utility Mod for auto collision/selection boxes for nodes with drawtype=mesh.
These auto-defined boxes come from its sister lua utility program, boxgen, in the form of <filename>.box files. These are placed in your mod's "data/" folder to be used with autbox's only function:
autobox.register_node(name, data_filename, node_definition, respect_nodes)
This function takes 4 parameters:
name name of the node, for example: "yourmod:example"
data_filename name of the node's box data, for example: "example.box"
node_definition This is your normal node_definition you provide to minetest.register_node()
respect_nodes Whether multi-node autobox nodes overwrite existing nodes or not
Putting it all together:
autobox.register_node("yourmod:example", "example.box", yournode_def, true)
Autobox is special because it allows modders (I believe for the first time) to create nodes using meshes larger than 3x3x3. Minetest has a restriction on mesh sizes of 3x3x3 for performance tradeoffs, and autobox allows us to represent larger meshes in a single-node-like way that respects this limitation.
Any mesh that is larger than 3x3x3 can have ".box" data generated with boxgen, and autobox will create "child nodes" that help represent the "parent node" you register.
When you dig, punch, rotate, or do anything to a child node, you will do it to all nodes connected with the parent, and vice versa. This allows them to act as a single node. But, to the user, child nodes will rarely be noticed.
When working with multi-node representations, it's important to realize that rotation can result in orientations where a child node might need to take the place of an existing node, like the ground when you spin a tower mesh updside down. In these cases, if you have registered your nodes with "respect_nodes"=true, the node will merely fail to rotate into the orientation and alert the rotating player why and where the rotation failed. This always occurs for protected nodes, even with respect_nodes = false.
Child_nodes are not in creative inventory, and should never be dropped in any way. If a player has access to a child node, they either hacked it in, or the server crashed just as the child nodes were being removed in some way.
To get a sample of what Autobox can let you do, uncomment the "init.lua" file's last line, which loads "example.lua". Then load up a creative world with autobox enabled and start placing and rotating and digging some "autobox:example" and "autobox:wagon" nodes to get a feel for the mod.