Jemison Biome Overhaul (Plus Tutorial)

While poking around the CK trying to learn about planet editing I realised that based on the work someone did reverse-engineering biome files, you can actually edit a planet's biome map fairly easily using a bit of Python code, With a little experimentation I managed to get new biomes I added to appear in-game and decided to give myself a project to see how far I could get with modding a planet in a weekend. I ended up learning how to do basically everything I wanted and was kind of surprised that no one else seems to have figured any of this out, so decided to release my weekend project as a small standalone mod for others to enjoy and to act as a demonstration of what's possible. Also included is a detailed guide on how I did everything so you can follow along and overhaul any planet you like. If you use it to make your own mod, please leave a comment with a link – I want to see it! Let a thousand worlds bloom!

Meet the new Jemison

Despite Jemison being one of the most important planets in the game, it only has a single unique biome for New Atlantis, while everything else is completely random – the mountains look like a different planet to the forests near New Atlantis, and the same mountains can be found on several other planets. In fact most planets are like this, with a single unique biome for hand-placed locations and a random selection of generic ones everywhere else. I found this really frustrating when surveying habitable planets because they're just a chaotic mishmash of random assets – in many cases two biomes right next to one other look completely unrelated, and animals and plants found on the same planet have no clear evolutionary relationships. So when I stumbled onto a way to replace default biomes with custom-made ones, I knew I had to try to one-up Todd, and redesign Jemison with an eye for detail, using an ecological story to guide the choices of landscapes, plants and animals to give Jemison a sense of place.

This redesign of Jemison is meant to represent a kind of idyllic, alternate Earth, using existing assets that resemble real animals. Like Earth was, Jemison is emerging from a global ice age and native lifeforms are rapidly diversifying into the new ecological niches as they open up. Most of the planet is covered in treeless grassland prairies, while more temperate regions in the mid-latitudes and coasts are home to the enormous mesa tree forests, in which New Atlantis sits. In the mountains, temperatures are still cold year-round, with spotty snow cover and a few small, hardy trees that can survive the chill. The ice caps, while rapidly receding, are largely barren.

During the ice age, Jemisonian animals had to evolve to deal with the extreme cold and are now re-adapting to the milder climate. The giant pseudosloths, bipedal herbivores the size of elephants that superficially resemble Old Earth's sloths, used an adaptation