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Post feature RSS Dev Diary 3 - Galaxy Generation

When you start a new game you can specify the size and shape of the galaxy as well as the number of (normal) AI empires. Sizes currently range from 200 - 1000 stars.

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Good news everyone!

Today we are going to share some details with you on how the galaxy is generated in Stellaris. When discussing this we will also touch on some of the different features of the galaxy and how we try to anticipate what modders will want to do with the galaxy generation in this game and making sure that they will be able to.

When you start a new game you can specify the size and shape of the galaxy as well as the number of (normal) AI empires. Sizes currently range from 200 - 1000 stars. The amount of AI empires only affects how many AI controlled empires that are generated from the start, a lot more will spring into existence during your game. Currently we have three different types of shapes for the galaxy; spiral, elliptical and ring. Spiral galaxies have the stars placed in arms that extend out in a spiral pattern (see “Pinwheel Galaxy”). A spiral galaxy provides an interesting geography, with voids between the arms that might be difficult to pass in a straight line. Elliptical galaxies have the stars placed in a ellipsoidal pattern (see Wikipedia), resulting in a more evenly distributed geography. Ring galaxies have the stars placed in a ring shape around the galaxy core (see “Hoag's Object”). If you play with a ring galaxy you know that other empires have to approach you either clockwise or counterclockwise within the ring, making it easier to cut other empires off from the rest of the galaxy than it is with any other shape. All of these options are of course moddable, both in regards to looks and available options.

Once you are satisfied with your options and decide to start the game, we begin the process of generating the galaxy. When we generate the stars we also decide what class each star should be. Most stars will be star classes with the different spectral types B,A,F,G,K,M. Some star systems can however be more special, like a black hole, pulsar or a neutron star. Every system with a certain star class has a given set of rules that controls how the star system is generated; you will, for example, have a hard time finding habitable planets close to a black hole. All of this is very moddable, you can add your own star classes and remove the existing ones if you want to.


We also generate some galactic features other than stars. One of these are nebulas. Nebulas are visible on the galaxy map and often contain a bunch of interesting star systems with special rare resources. In a nebula you can expect to encounter some special events and experience certain penalties and bonuses that may impact your decisions when it comes to colonization and fleet movement.

When we generate the contents of each star system we use different system initializers depending on what the system is being used for. If you, for example, were to start as a pre-scripted human you will be placed in our solar system, on Earth. Yes, all of this is moddable also. These initializers allow us to make sure that you, as a player, will always have something interesting to do within a system. They also provide us with ways to create a more balanced start, by being able to affect the content of your star system and systems that are neighboring to yours. It is worth knowing that these initializers have a certain random factor attached to them, so you should never expect the exact same setup between game sessions.

We generate a lot of interesting special content in the different systems, including the ones that no empire is controlling. This content ranges from debris to ships of unknown origin, that could be friendly or not so friendly... Speaking from personal experience when it comes to the “not so friendly” ships, I recommend all players to scout systems before going there with their science ships to survey a potential future colony. It is not fun having your science ship blown out of existence with your most skilled scientist aboard.


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