PS_View is a PostScript and PDF previewer. It is multiplatform (Windows, Linux and Mac OS X), GUI program based on the Ghostscript engine. Key features include huge magnification, fast viewing of large documents, exact measuring, and restart.
Emma (Extensible Multi Media Architecture) is an open-source, modular, extensible, dynamic framework for declarative authoring and display of 2D and 3D interactive multimedia. It uses Lua for scripting and Ogre3D for rendering. http://www.emma3d.org