This script is an add-on for Blender 4.2 that allows users to create customized legends and overlay them onto their renders in real-time using Blender's compositor. Thanks to the powerful real-time compositor introduced in Blender 4.2, this add-on is particularly useful for scientific visualization, where precise and customizable legends are essential.

1. Requirements
2. Features
3. Installation
   • Important Note: Blender Installation
   • Install Blender 4.2
   • Install matplotlib
   • Install the Add-on
4. Usage
   • Accessing the Legend Generator Panel
   • Configuring Your Legend
   • Adding and Configuring Color Nodes
   • Generating the Legend
   • Integrating the Legend into Your Render
5. Contributing

Before installing Blender and the add-on, ensure that you meet the following requirements:

1. Operating System:

   • Linux (any recent distribution)

2. Blender:

   • Blender 4.2 or higher

3. Python:

   • Python 3.11 (bundled with Blender 4.2)

4. Disk Space:

   • At least 1 GB of free disk space for Blender installation and dependencies.

5. Internet Connection:

   • Required to download Blender, matplotlib, and other dependencies.

• Customizable Legends: Generate gradient-based legends with various interpolation methods.
• Real-Time Compositing: Integrate the legends directly into your renders using Blender's compositor.
• Easy to Use: Configure and apply legends directly within the Blender interface.
• Scientific Colormaps: Choose from a variety of built-in scientific colormaps or use custom colors.
• Flexible Positioning: Easily adjust the position and scale of the legend in your render.
• Font Customization: Use system fonts or custom font files for legend text.
• Text Color Control: Adjust the color of the legend text to match your render style.
• Orientation Options: Create both horizontal and vertical legends.

IMPORTANT: When installing Blender, it is crucial to avoid using the Snap package version. The Snap version of Blender creates an isolated environment that prevents the installation of additional Python packages like matplotlib, which is essential for this add-on to function correctly.

Instead, please follow the manual installation instructions provided below to ensure that you can properly install and use all required dependencies.

Follow these steps to install Blender 4.2+ based on your operating system:

Disclaimer: The following commands are specifically for Blender 4.2.1. If you are using a different version of Blender, simply replace 4.2.1 with the version you are using (e.g., 4.2.0, 4.3.0, etc.).

1. Download Blender 4.2.1:

   • Go to the official Blender website: Blender Download.
   • Download the Blender 4.2.1 version for Linux (as a .tar.xz file).

2. Extract Blender:

   • Open a terminal and navigate to your Downloads directory:

     cd ~/Downloads

   • Create a directory for Blender and extract the downloaded file:

     sudo mkdir -p /opt/blender
     sudo tar -xvf blender-4.2.1-linux-x64.tar.xz -C /opt/blender/

   • Change the ownership of the Blender directory:

     sudo chown -R $USER:$USER /opt/blender

3. Create a Symlink for Easy Access:

   • Create a symbolic link to run Blender easily from the terminal:

     sudo ln -s /opt/blender/blender-4.2.1-linux-x64/blender /usr/local/bin/blender

   • Now you can run Blender by typing blender in your terminal.

1. Download Blender 4.2.1:

   • Go to the official Blender website: Blender Download.
   • Download the Blender 4.2.1 version for macOS.

2. Install Blender:

   • Open the .dmg file and drag Blender to your Applications folder.

3. Run Blender:

   • You can launch Blender directly from the Applications folder or by typing open /Applications/Blender.app in the terminal.

1. Download Blender 4.2.1:

   • Go to the official Blender website: Blender Download.
   • Download the Blender 4.2.1 installer for Windows.

2. Install Blender:

   • Run the .exe installer and follow the installation prompts.

3. Add Blender to PATH (Optional):

   • If you want to run Blender from the command line, make sure to check the option to add Blender to your system's PATH during installation. Alternatively, you can manually add the Blender installation directory to the PATH environment variable.

4. Run Blender:

   • You can launch Blender from the Start menu or by typing blender in the command prompt (if added to PATH).

To ensure the add-on functions correctly, you need to install matplotlib in Blender's Python environment. The steps are the same across Linux, macOS, and Windows:

1. Ensure pip is Available:

   • Run the following command to ensure pip is installed in Blender's Python environment (replace the path with your Blender 4.2.1 installation path):

     <path_to_blender>/4.2.1/python/bin/python3.11 -m ensurepip

2. Install matplotlib:

   • Install matplotlib using pip within Blender’s Python environment. Be sure to target Blender's Python site-packages folder:

     <path_to_blender>/4.2.1/python/bin/python3.11 -m pip install --target=<path_to_blender>/4.2.1/python/lib/python3.11/site-packages matplotlib

3. Upgrade if Necessary:

   • If you encounter package conflicts or warnings, use the --upgrade flag:

     <path_to_blender>/4.2.1/python/bin/python3.11 -m pip install --target=<path_to_blender>/4.2.1/python/lib/python3.11/site-packages --upgrade matplotlib

1. Package the Script:

   • Place the provided script files into a folder named LegendGenerator.

2. Install the Add-on in Blender:

   • Open Blender and go to Edit > Preferences > Add-ons.
   • Click on Install... and select the LegendGenerator folder.
   • Enable the add-on by checking the box next to Legend Generator.

3. Using the Add-on:

   • Access the add-on from the View3D panel under the Legend Generator tab.
   • Configure your legend and add it to your composition.

Once the add-on is installed and enabled, you can use it to generate and customize legends in Blender. Here's a step-by-step guide on how to use the add-on:

• Open Blender and switch to the 3D Viewport.
• In the right sidebar, you will see a new tab called Legend Generator.
• Click on this tab to access the add-on's UI panel.

• Number of Nodes: Specify the number of color nodes for your gradient. This controls the complexity of the gradient used in the legend.
• Legend Name: Enter the name of the legend. This will appear as the label on the legend bar.
• Interpolation Method: Choose how the colors between nodes are interpolated. Options include:
  • Linear: Smooth transition between colors.
  • Stair Step: Abrupt changes between colors, useful for categorical data.
  • Cubic: Smooth cubic interpolation.
  • Nearest: Colors are assigned to the nearest node without interpolation.
• Orientation: Choose between horizontal and vertical legend orientation.
• Colormap: Select from built-in scientific colormaps or use custom colors.
• Colormap Range: Set the start and end values for the colormap and adjust the number of subdivisions.

• In the Legend Generator panel, you will see a list of color nodes.
• For each node, you can set a color and an associated value (label).
• You can rearrange the nodes using the Up and Down buttons to adjust the order in the legend.
• When using a scientific colormap, the color nodes will be automatically generated based on your settings.

• Legend Dimension: Set the width and height of the legend in pixels.
• Scale: Adjust the scale of the legend relative to the scene or render size. You can link or unlink X and Y scaling.
• Position: Set the X and Y position of the legend in your render.
• Font: Choose between system fonts or a custom font file for the legend text.
• Text Color: Set the color of the legend text to match your render style.

• Once configured, click the Generate Legend button.
• The legend will be generated as an image and automatically added to your compositor in Blender.

• The generated legend will appear as a new image node in the compositor.
• The add-on automatically sets up the necessary nodes to overlay the legend on your render.
• You can further adjust the position and scale of the legend using the controls in the Legend Generator panel.

Contributions are welcome! Feel free to open issues or submit pull requests to improve this project.