Blender Python Add-on Development

This skill covers building Blender add-ons with the bpy API, including add-on structure, operators, panels, properties, safe scene manipulation, and testing across Blender versions.

Workflow for Building a Blender Add-on

1. Scaffold the add-on — Create a package with __init__.py as the entry point, and a blender_manifest.toml (Blender 4.2+ extensions) or bl_info dict (legacy add-ons) describing name, version, and supported Blender version.
2. Define data — Create PropertyGroup classes for grouped settings and register them on the appropriate ID type (e.g., bpy.types.Scene.my_addon = PointerProperty(type=MyAddonSettings)).
3. Implement operators — Subclass bpy.types.Operator for each user action; implement poll() for availability, invoke() for interactive setup, and execute() for the actual work.
4. Build UI panels — Subclass bpy.types.Panel to expose operators and properties in the appropriate editor (3D viewport sidebar, properties editor, etc.).
5. Register everything — List all classes in a classes tuple and register/unregister them in matching register()/unregister() functions; register property pointers alongside their classes.
6. Test in a clean profile — Launch Blender with --factory-startup, install the add-on, enable it, exercise each operator, then disable it and confirm nothing is left behind.
7. Package and ship — Zip the add-on folder (or build a .zip extension package) and verify it installs cleanly via Blender's Preferences > Add-ons (or Extensions) panel.

Add-on Structure