Papervision is the first Flash 3D framework that’s gained real traction in the dev community. The code is well organized and documented which makes a nice change. Also there is a lot of active development happening, including an AS3 version in the works.
You can download the ribbon source code here. To use this source, you will first need to download the Papervision code using an SVN client. Once you’ve downloaded papervision, copy over the contents of the zip file.
If you’re using Eclipse, the easiest way grab papervision is to install Subclipse, then do a File -> Import -> ‘Checkout Projects from SVN’. Enter the repository URL: http://svn1.cvsdude.com/osflash/papervision3d. Eclipse will create a new project for you and download the files.