Blender Extension Developer 101 | ECOSYSTEM Research

Building a custom Blender extension (or add-on) is a great way to automate tasks or create new tools. Since you already work with C++, JUCE, and Rust, picking up Blender's Python API will be straightforward, as it's highly structured and declarative. Here is a complete guide to setting up your environment, writing the code, and seeing your new tool in action. 1. Setting Up Your Development Environment While you can write scripts directly in Blender, using an external IDE like VS Code is much more efficient for proper extensions. 1. Install VS Code & Python: Ensure you have Python installed, as Blender uses it for all its scripting. 2. Install the Blender Development Extension: In VS Code, search for and install the Blender Development extension by Jacques Lucke (id: JacquesLucke.blender-development). This extension handles linking your code to Blender, reloading scripts, and debugging. 3. Create Your Workspace: Create a new folder for your project (e.g., myblenderaddon). Open this folder in VS Code. 4. Connect to Blender: Press Ctrl+Shift+P (or Cmd+Shift+P on Mac) and type Blender: Start. Choose your installed Blender executable. The extension will start Blender and automatically link your workspace folder as an add-on directory. --- 2. The Anatomy of an Add-on A minimal Blender add-on requires three things: 1. blinfo metadata: Tells Blender the name, author, and version. 2. Classes: The actual operators (actions) or panels (UI) you want to create. 3. register() and unregister() functions: How Blender loads and unloads your code. Create a file named init.py in your workspace folder. This tells Python (and Blender) that this folder is a module. Step 1: Add the Metadata At the top of init.py, define your blinfo dictionary. This is what shows up in Blender's Preferences Add-ons menu. Step 2: Define an Operator (The Action) Operators are the functions that actually do things in Blender. They inherit from bpy.types.Operator. We'll create one that spawns a cube. Step 3: Define a Panel (The UI) To give the user a button to click, we need a Panel. This is a declarative class that tells Blender where and how to draw the UI. We'll place it in the 3D Viewport's sidebar (the "N" panel). Step 4: Register and Unregister Blender needs to be told about your custom classes so it can integrate them into its internal systems. We do this by creating a list of classes and iterating through them. --- 3. Running and Testing 1. Save the file. 2. If you started Blender via VS Code, press Ctrl+Shift+P and select Blender: Reload Addons. 3. In Blender, hover your mouse over the 3D Viewport and press N to open the sidebar. 4. You should see a new tab called Spawner Tab. Click it, and you'll find your Add Cube button. Pro Tips for Blender Scripting Info Editor: If you want to know how to do something in Python, do it manually in the Blender UI first. Pull down the Info Editor (usually hidden at the very top or bottom of the screen). Blender logs the exact Python commands for almost every action you take. You can copy those commands directly into your script. Context: Notice the context argument in the execute and draw functions. This gives you access to the current state of Blender—what object is selected (context.activeobject), what scene you are in, etc. Console Logging: Standard Python print() statements won't show up in Blender's UI. You have to open the system console (Window Toggle System Console) to see them, or use self.report() to push messages directly to Blender's interface.