Blender Addon Structure

The Blender addon is a series of Python files in the extension directory.

• __init__.py is the entrypoint to the entire addon
• blender_manifest.toml contains the packaing information for the addon
• Any file that starts with op_ contains a Blender Operators.
• skein_panel.py is the Panel UI for Objects, Meshes, and Materials
• gltf_export_extension is the glTF export extension code that handles setting the glTF extras
• property_groups.py is the core of the Component's data.
• form_to_object.py is basically PropertyGroup.to_json() (this "to_json" doesn't exist afaik)
• object_to_form.py is the opposite of form_to_object.py. It takes JSON data and inserts it into a Component.
• CLI extensions are prefixed with cli_

The Workflow

Workflow-wise, the FetchRemoteTypeRegistry operator must be run to fetch the Bevy registry data, which means it must be the first action before being able to insert and modify Component data on objects.

FetchRemoteTypeRegistry will store the result of a Bevy Remote Protocol request in a skein-registry.json text file. Future opens of the .blend file will load the registry data from skein-registry.json instead of needing to make a BRP request.

Processing the Registry

After gaining access to the registry information, we build PropertyGroups dynamically for every single Component type and, because Blender Properties require static typing and don't support rich enums, we build out a large container type that contains a field for every single Component type. The container component type stores information about which Component it is supposed to represent, which is then used to pick the right fields to display in the UI.

Having this large container type allows us to set up a CollectionProperty that can support multiple Components.

Inserting Components on Objects, Meshes, or Materials is as easy as inserting one of these container types into the Components CollectionProperty on the object, mesh, or material.

The Skein Panel UI

The SkeinPanel will then introspect the data in the CollectionProperty's PropertyGroups to build forms for the selected Component data.

Using these PropertyGroups is what allows us to take advantage of Blender features like Drivers and Library Overrides.