All connected buildings will attempt to share and transfer commodities with each other where needed. Processing industries will fetch raw resources from resource harvesting industries, and factories will fetch the processed materials to make their products. This is all automatic once the trade connection between the buildings is established.
There is no automatic trade connection between solar systems. Trade between solar systems has to be setup with shipments or cargo ships.
In order for buildings to share commodities with eachother a trade connection is required with each other. There's five different types of trade links:
- Neighbor connection
- Two buildings that are within ?m of each other are considered connected.
- Road connection
- Road can connect buildings over a greater distance cheaply. All buildings near the road will be connected.
- Sea connection
- A building connected to a wharf will be connected with all other buildings also connected to a wharf on the same world.
- Air connection
- A building connected to an airport terminal will be connected with all other buildings also connected to a airport terminal on the same world.
- Space connection
- A building connected to an airport terminal will be connected with all other buildings also connected to a airport terminal in the same solar system.
A trade connection even works while a wharf or an airport terminal is still under construction.
Buildings fetch commodities they need from other connected buildings. This is the same for construction, manufacturing and impoting.
For example: a machine shop producing hammers using metal will attempt to fetch metal from any connected building, be it from a smelter, warehouse or any other building that might have any.
A commodity might be wasted when fetched if it fails a quality check.
Some buildings import specific commodities in order to have them available for sale or to assist connected buildings.
In order to prevent cities from losing essential commodities to other cities, buildings in certain environments reserve a minimum stock of some commodities:
- Air, Water - On a world that does not support animal life, a building reserves 13 units per citizen.
- Food - On a world that does not support plant life, a city reserves 10 units of each kind of food per citizen, divided by its food value.