File system

Introduction

File systems are yet another hot topic in engine development. The file system manages how the assets are stored, and how they are accessed. A well designed file system also allows multiple developers to edit the same source files and assets while collaborating together.

Initial versions of the Godot engine (and previous iterations before it was named Godot) used a database. Assets were stored in it and assigned an ID. Other approaches were tried as well, such as local databases, files with metadata, etc. In the end the simple approach won and now Godot stores all assets as files in the file system.

Implementation

The file system stores resources on disk. Anything, from a script, to a scene or a PNG image is a resource to the engine. If a resource contains properties that reference other resources on disk, the paths to those resources are also included. If a resource has sub-resources that are built-in, the resource is saved in a single file together with all the bundled sub-resources. For example, a font resource is often bundled together with the font textures.

In general the Godot file system avoids using metadata files. The reason for this is simple, existing asset managers and VCSs are simply much better than anything we can implement, so Godot tries the best to play along with SVN, Git, Mercurial, Perforce, etc.

Example of a file system contents:

/engine.cfg
/enemy/enemy.scn
/enemy/enemy.gd
/enemy/enemysprite.png
/player/player.gd

engine.cfg

The engine.cfg file is the project description file, and it is always found at the root of the project. In fact it’s location defines where the root is. This is the first file that Godot looks for when opening a project.

This file contains the project configuration in plain text, using the win.ini format. Even an empty engine.cfg can function as a basic definition of a blank project.

Path delimiter

Godot only supports / as a path delimiter. This is done for portability reasons. All operating systems support this, even Windows, so a path such as c:\project\engine.cfg needs to be typed as c:/project/engine.cfg.

Resource path

When accessing resources, using the host OS file system layout can be cumbersome and non-portable. To solve this problem, the special path res:// was created.

The path res:// will always point at the project root (where engine.cfg is located, so in fact res://engine.cfg is always valid).

This file system is read-write only when running the project locally from the editor. When exported or when running on different devices (such as phones or consoles, or running from DVD), the file system will become read-only and writing will no longer be permitted.

User path

Writing to disk is often still needed for various tasks such as saving game state or downloading content packs. To this end, the engine ensures that there is a special path user:// that is always writable.

Host file system

Alternatively host file system paths can also be used, but this is not recommended for a released product as these paths are not guaranteed to work on all platforms. However, using host file system paths can be very useful when writing development tools in Godot!

Drawbacks

There are some drawbacks to this simple file system design. The first issue is that moving assets around (renaming them or moving them from one path to another inside the project) will break existing references to these assets. These references will have to be re-defined to point at the new asset location.

The second is that under Windows and OSX file and path names are case insensitive. If a developer working in a case insensitive host file system saves an asset as “myfile.PNG”, but then references it as “myfile.png”, it will work just fine on their platorm, but not on other platforms, such as Linux, Android, etc. This may also apply to exported binaries, which use a compressed package to store all files.

It is recommended that your team clearly defines a naming convention for files when working with Godot! One simple fool-proof convention is to only allow lowercase file and path names.