Terraforming is the act of changing the planet classification of a celestial body in order to make it more habitable for the empire's species. The base technologies requires significant society research to unlock and each terraforming project requires significant investments of Energy and time.
Terraforming is started via a button in Planet Detail view. The world must be surveyed and within your borders. Only habitable worlds, and Barren Worlds that have the rare "Terraforming Candidate" modifier, can be terraformed. The expansion planner screen can be used to find these rare candidates.
Ecumenopolis worlds are created via decisions rather than terraforming. They must be inhabited but pops do not suffer a happiness penalty during the process.
The following planet modifiers are always removed when terraforming a planet:
When and if terraforming a planet to Hive or Machine World, keep in mind that all planetary features, excluding a few rare ones that give access to rare resources, will always be removed.
Cost reduction & speed
Terraforming cost can be affected by the following: