Wikipedia defines 3-D this way:
3D (three-dimensional) film is a motion picture that enhances the illusion of depth perception. Derived from stereoscopic photography, a special motion picture camera system is used to record the images as seen from two perspectives and special projection hardware and/or eyewear are used to provide the illusion of depth when viewing the film.
So basically its an illusion created before your eyes that provides a view from two perspective angles. This can be achieved either by shooting the entire film using a costly two eyed camera capable of capturing 3D motion picture or by converting an ordinary 2D video by providing it an angled perspective after production. The former was used in ‘Avatar’ and the latest ‘Resident Evil’ movie. It’s the ultimate experience you can achieve from a 3D technology. Using latter 3D stereo rendering only a small depth of field change can be achieved.
Another important un avoidable hardware in the 3D technology is the glasses used. Without which you cannot view and enjoy the 3-D videos. Based on the architecture even there exists different variety of 3D glasses. The first and the most cheapest glass format being the coloredAnaglyph glass.
Some common types of 3D glasses are:
1) Anaglyph – Red Blue glasses ( Cheap and common ) –
2) Active shutter glasses –
3) Polarized 3D glasses
Being the cheapest option available and easily attainable 3D video rendered outputs we are concerned with the Anaglyph Red Blue 3D glasses here. Check out the below pic to understand how 3D technology using Anaglyph glasses work.