The magic effect of flat images becoming three-dimensional is known as 3D effect. 3D imagery has been around for ages, mostly as a gimmick. But in the past few years a 3D technology has matured and became popular in masses mainly due to the success of adventurous sci-fi movie Avatar and some other Hollywood blockbusters. Each day three-dimensional technology fascinates more and more viewers, with its number of fans continuously growing. Avatar's director James Cameron even predicts 100% 3D expansion in few years both in cinemas and at home. So what's this magic technology about and how does it actually work?

How 3D works in your everyday life.The 3D technology is based on the human's ability to see the world around us in three dimensions. This ability is caused by the actual distance between our eyes, that enables each eye to see slightly different image. That's easy to notice when you look at an object and alternately close one of your eyes. With each eye you see an object from a slightly different perspective. The two different images, two layers of an object viewed by your eyes are then transmitted to your brain, where they combine in the process called brain fusion. As a result your brain perceives a merged three-dimensional image thus a 3D object.

How 3D is used in movies and videos.The idea behind 3D movies and videos is based on the delivery of the left picture to the left eye and the right image to the right one. 3D image can be viewed by three different methods: with passive (anaglyph red/cyan or polarized) glasses, with active (shutter) glasses and with no glasses at all (parallax barrier). Let's take a brief look at each of them.

Passive glasses (Anaglyph red/cyan or polarized glasses)

In anaglyph method two images (one colored in blue and the other - in red) are projected onto a screen and imposed one upon the other. Each colored lens of anaglyph glasses blocks a layer of the image for the eye it is covering: red lens - for the left eye, blue lens - for the right. Thus each eye sees its corresponding image, two images than are combined in our brain for three-dimensional image.

Polarized 3D glasses work similar to anaglyph colored glasses, but are slightly different. This method lies in the concept of polarization of light that as we know spreads in waves. So passive polarized 3D glasses have special polarizing filters in each lens that block out certain light waves, thus a certain image for each eye. An example of such passive 3D glasses are RealD polarized glasses you are given in cinemas.

Active glasses (Shutter glasses)

Method of 3D viewing through active 3D glasses has a different approach. Active 3D glasses need electricity to work, so they are normally equipped with small batteries. Liquid crystal layers for each eye are integrated into such glasses and work as shutters that can be driven either transparent or opaque by applying voltage. Such "shutter" glasses work in synchronization with the projecting system, which shows different frames for each eye. The glasses open and close "shutters" in turns for each eye to get its corresponding image. Such synchronization between the active 3D glasses of the viewer and the projecting system is controlled by wireless signals.

No glasses (Parallax Barrier)

The third method uses no glasses and is based on putting a special filter known as parallax barrier onto a screen, e.g. of LCD panel. Again we have two images, which are broadcasted on the screen, each with a slightly different perspective. Parallax barrier has a series of slits that allows each eye to see different set of pixels for each perspective. Our brain then processes two images and perceives them as one 3D image.

Which of these methods will prevail is hard to tell. But what we know for sure there is already a number of 3D software, so-called stereoscopic players, that enable you to watch any video or movie in 3D. These are very popular nowadays, especially for home 3D experiences, and require only your PC and 3D glasses to view the 3D effect. Most convenient one is 3D Video Player, download it for free here

Here's a scheme with all three methods visualized (image courtesy of OnlineSchools.org)