Unity is a game engine made by Unity Technologies. It supports more than 25 different platforms. This engine is used mostly to design three-dimensional, two-dimensional, virtual reality, and augmented reality games. It has been adopted not only by video gaming industry, but also by film, automotive, architecture, engineering and construction.
Unity enables users to develop games and experiences both in 2D and 3D, and offers a primary scripting API in C#, as well as drag and drop functionality. Within 2D games, Unity provides importation of sprites and a 2D world renderer. For 3D games, it allows specification of texture compression, mipmaps, and resolution settings for each platform it supports. Also, it provides support for bump mapping, reflection mapping, parallax mapping, screen space ambient occlusion, dynamic shadowing, render-to-texture and full-screen post-processing effects.
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.