Universal 3D (U3D) is a compressed file format standard for 3D computer graphics data.
The format was defined by a special consortium called 3D Industry Forum that brought together a diverse group of companies and organizations, including Intel, Boeing, HP, Adobe Systems, Bentley Systems, Right Hemisphere and others whose main focus had been the promotional development of 3D graphics for use in various industries, specifically at this time manufacturing as well as construction and industrial plant design. The format was later standardized by Ecma International in August 2005 as ECMA-363.
The goal is a universal standard for three-dimensional data of all kinds, to facilitate data exchange. The consortium promoted also the development of an open source library for facilitating the adoption of the format.
3D PDF is a PDF file with 3D geometry inside. Using any 3D PDF enabled viewer, rotation, zoom and part selection is available within the 3D view.
3D PDF is just like a normal PDF (Portable Document Format) file, which contains a 3D view somewhere on some page. Just like a PDF containing an embedded image, except when you put the mouse over it, you can rotate, zoom, pan and explore the scene in 3D (three dimensions). The file actually contains a 3D geometric representation of the scene, not just images from different viewpoints.