There is only one file type that uses the .W3D extension:
Adobe Shockwave 3D File
File used by Adobe Director, a program used for making interactive multimedia content for the Web, CDs, and DVDs; stores a 3D scene and/or animation that was exported from a third-party 3D modeling program and then imported into Adobe Director for publishing online.
W3D files can be incorporated into Adobe Director movie project (.DIR file) or referenced by a Shockwave multimedia application that has been published to the Web. They are played with the Adobe Shockwave Player, which was replaced by Adobe's Flash Player.
NOTE: Intel and Macromedia (acquired by Adobe Systems) jointly created the W3D format. It was designed to allow third-party 3D modeling tools to export 3D scenes and then stream them on the Web using the Shockwave Player.
Updated: October 23, 2012