Wessel Stoop


The Sapling was built from the ground up with community interaction in mind. This interaction goes both ways: players can take stuff generated by or for the game, and use it in their own creations, or they can add their own creations to the game.

This article functions as an in-depth guide on how to do this, to be used as reference. It's a living document that will be updated continuously. If you find any things that are unclear or just incorrect, or have more ideas you want to share with other creators, drop me a line at .

Overview of the information on this page:

  1. Repurposing material from the game
    1. Music
    2. Exporting lifeforms and animations generated by the game
    3. Using gameplay statistics from the API
  2. Extending the game
    1. Scenarios
    2. Body parts
    3. How to create asset bundles

1 Repurpose material from the game for your own creations

Reusing material from the Sapling for non-commercial creative purposes is highly encouraged. These three things should help with that:

1.1 Music

The music in the Sapling is generated on the fly by combining smaller parts. If you are a musician, you are encouraged to reuse them; for example in remixes and mashups. The sheet music could be the basis for covers. I'd love to see your project; let me know at .

1.2 Exporting lifeforms and animations generated by the game

Pressing the e button in the plant or animal editor will create a .obj file in the game's persistent storage location. On Windows, this is most likely C:\Users\YourUserName\AppData\LocalLow\Wessel Stoop\The Sapling , on Mac and Linux it is probably ~/Library/Application Support/Wessel Stoop/The Sapling . The .obj file contains the 3D model of your animal, and can be imported by most (all?) 3D modeling software. In game, these models are softened with one layer of Catmull-Clark subdivision, so you might also want to do that in your modeling software.

In the animal editor, a number of .json files are also created besides the .obj file:

The JSON format can easily be interpreted by any programming language, so it should be easy to write a script to import it to your 3D animation software of choice. I use free animation software Blender with Python as a scripting language; a setup for importing animals and their animations can be found here.

1.3 Using gameplay statistics from the API

To get a better understanding of the way people play the game, various gameplay statistics are collected anonymously. They are saved in the form of events, logged in a separate file per IP address. Examples of events are:

I hope to have set up this system in such way that I can turn these raw data into useful statistics as soon as I have a quantitative question in the future. However, this dataset is much too interesting to keep for myself. For that reason, the data are also available as a simple API. If you're interested, you can use this data to create things like pretty infographics, realtime dashboards, interactive visualizations, you name it.

For an overview of recorded sessions, visit . This will give a long lists of IDs. To see the collected events for a particular ID, you need to visit: ; one line is one event. Please note that this URL will change in the near future.

2 Extending the game

To create a new scenario or a new bodypart essentially means to create a 3D model, an icon and some configuration. These files are not 'packaged' with the main files of the rest of the game, but instead in separate so-called 'Unity asset bundles'; one scenario/bodypart per bundle. You can find these bundles in the the_sapling_Data/Resources/ folder. Adding scenarios and bodyparts simply means creating more of these bundles.

Below you will find an overview of what files need to go into what bundle. Besides this overview, you can download this zip containing the files used for the bundles included in the vanilla game as an example.

2.1 What you need for a scenario asset bundle

In the game's files, the various scenarios are identified with a number: the first four main scenarios are called 0, 1, 2 and 3. This numbering is also used to order the scenarios. To prevent clashes with future main scenarios or other custom scenarios, it's probably best to give your custom scenario a 2-digit identifier.

2.2 What you need for a bodypart asset bundle

To get your bodypart working, you need to add your bundle to the correct subfolder of the the_sapling_Data/Resources/Bodyparts folder. The subfolder you choose defines as what kind of bodypart (is this a leaf or an eyeball?) your creation will be interpreted.

2.3 Packaging your files into a bundle

When you have all the files you need, finally you will need to convert them to Unity asset bundles. These are the steps:

  1. Download Unity. I have used Unity 2017.1.0f3, but probably any version of Unity will do.
  2. Download this Unity project where everything you need is already preconfigured. Alternatively, you can set up your own by following Unity's instructions; in that case the rest of these instructions don't apply.
  3. Load the folder with the files for the new scenario or bodypart into the project; for example by simply dragging it in.
  4. For each of the files, select them in project window, and then go to the inspector window. Here, you should see an AssetBundle dropdown. Create a new AssetBundle for the first file, and make sure the rest of all your files are in this same bundle.
  5. In the top menu, Assets > Build AssetBundles. The files will now appear in the AssetBundles folder inside the Unity project. From here, you can move them to the correct subfolder of the game files.

Published Thursday 21 November 2019