Valve Development Tools for Blender
- Support for Blender 2.66 or later versions only.
Blender SMD tools
Valve has provided an addon srouce Tools package as a .zip file, which can be downloaded at the following location: 
- Install Blender 2.66 or later.
- If you have not downloaded the Source Tools above (link here: ), remember not to unzip. Blender needs the entire .zip file unmodified for the installation process.
- In Blender:
- Select File > User Preferences
- Move to the Addons tab
- Click Install From File (bottom of the window)
- Find the downloaded zip file
- Find and check the Source Tools’ box. Wait a moment for activation to complete.
- Click Save User Settings.