How does 3D work?

With all this talk of upcoming 3D gaming, 3D movies, and 3D television, I think its a little important to understand how 3D works. For the sake of post length, I'll not be going into depth (haha... perception joke) with this.

Obviously, 3D refers to the ability of images to create the illusion of depth perception. In other words, the illusion that what you're seeing is "really there". This illusion is created through a technique known as stereoscopy (you've seen this word before, no doubt), which shows two images, one to each eye. Each image is from a slightly different perspective, the right one is slightly farther to the right than the left one, for example. When your eyes perceive these two images at the same time from the correct angle, the illusion of depth is created.

This technique has remained relatively unchanged since it was invented by Sir Charles Wheatstone in 1838. The original stereographic images required no glasses or other viewing aid, they required the viewer to simply cross their eyes at the right distance from the page. A stereoscope, a device that looks somewhat similar to a pair of glasses, exists for viewing these images as well. The steroscope utilizes lenses to magnify the images in such a way that the viewer no longer needs to cross their eyes, reducing eye strain and making the viewing of stereoscopic images much more easy.



Today, many more techniques exist for fooling our eyes. After the 3D movie craze of the 1950s, most people are familiar with the red/blue (or green) 3D glasses. The movie itself is shot on two cameras, spaced next to one another the same distance that the human eyes are spaced. This is important, because if the spacing is off, than the images will not look correct when our brains try to put the images together later. In post-production, the film from one camera is passed through a red filter and the film from the other camera is passed through a green or blue filter. Then, these images are placed together again in the final film with the same offset in which they were shot. When the light from the movie reaches your eyes, each lens filters out the opposite color and you'll only see one camera's point of view. The obvious downside to this is that you can't really watch color films, since the whole gimmick relies on red and blue (or green).



The same technique is used for those fancy polarized 3D glasses that you see in movie theaters today. Two different images are shown on the screen, but they involve polarized light that will be filtered out by each lens. The obvious advantage to this system is that movies can be shown in color, since is relies on blocking certain polarized light. (Think of it as being similar to polarized sunglasses.)



Now, the concept of 3D gaming is by no means a "new" or "innovative" concept, despite what the other blogs say. The original Sega Master System supported 3D with a peripheral known as "SegaScope 3-D Glasses". These were LCD shutter glasses that connected to the system itself with a wire. This technique (known as Alternate-frame sequencing) is also used in a lot of 3D televisions today, like Sony's Bravia 3D televisions. The way it works is the lenses rapidly alternate between the left and right being opaque, at the same time the images on the television alternate between left and right. This technique requires the glasses and television to be "in-tune" with one another. In the case of the SegaScope glasses, the wired connection to the Master System allowed them to be regulated to the correct timing sequence. Today's glasses are kept in tempo with infared so that they can be wireless. Unfortunately, this 3D technique requires the glasses to have a power source, so if you forget to charge them, you can't have 3D.



More famous (or perhaps infamous) is Nintendo's Virtual Boy. This eyepiece-shaped console used a technique called parallax to imitate depth. Images in the foreground were farther apart between the two screens, and images meant to be far away from the user had little to no offset. Red LED pixels were chosen to create the display because they were the least expensive, drained the battery less, and were more visually striking. A color version was tested in development, but users complained that it just made them see double instead of 3D.



This brings me to another one of the newer 3D techniques (and frankly, the one I'm most excited to see) called Auto 3D. All of the other techniques used for 3D movies require lenses or special glasses to help separate the images. Not with Auto 3D, which is short for Autostereoscopic. This technique relies on special lenses in the television itself that redirect images for each eye to different viewing zones in front of the television. The obvious downside to this is that if you aren't sitting at the exact right viewing position, you won't see in 3D. One of the fixes to this is tracking the eyes of the viewer, so that even if they move, the television moves the viewing point with them. (I think this is what Nintendo will end up doing with the 3DS.)



I did leave out quite a bit of information. You can read a lot more about 3D at howstuffworks and Wikipedia, which are where I got many of these helpful diagrams. If I got something wrong, be sure to correct me. Thanks for reading!