Monday, February 17, 2014

3D Just Wants to be Understood...

Before you may read any further into this article you must first pass the 3D vision test provided below. It has been recorded that approximately 12% of people are unable to properly see 3D images due to a variety of medical conditions. Namely blindness.  The Test

If you're reading this then Congratulations! Looks like you're part of the 88% of us that can properly view 3D images. Lately 3D technology is all the rage. You can watch it, create it, or use it. There are 3D printers, 3D glasses, 3D movies, 3D games, 3D Wallpaper, 3D animation, 3D modeling software-- well, you get the picture.

I'm not here to tell you whether or not 3D technology is sent from heaven or hell. Instead, I'd like to bestow upon you some information that may help back your stance (whatever it is) in future debates.

Let's first take a look at how eyes work. You know how an image will move slightly depending on which eye you're using? That's because our eyes are spaced about 2 inches (5 centimeters) apart. Therefore, each eye sees the world from a slightly different perspective. BUT WAIT--  if our eyes are each seeing a different image, how come we only see one image when both eyes are open?

Good question reader! As your brain collects the information provided by each eye, it uses the difference to calculate distance. Just like how a stereo track in audio contains all of the audio information in one track, your brain has the ability to correlate the images it sees in its two eyes-- despite the fact that they are slightly different.

Now that we understand how our eyes determine depth and distance accurately, let's take a look at all the different types of 3D glasses on the market today.

Two main categories of 3D glasses are active viewers and passive viewers 

ACTIVE VIEWERS: 3D glasses that interact electronically with the display

  • good 3D effect
  • expensive
  • not very comfortable
  • flickering can cause dizziness

  • Active viewer glasses tend to be more bulky than passive view glasses

Active View glasses create the illusion of depth and 3D through the use of liquid crystal shutter systems. The shutter system works by openly presenting the image intended for the left eye while blocking the right eye's view, then presenting the right-eye image while blocking the left eye, and repeating this so rapidly that the interruptions do not interfere with the perceived fusion of the two images into a single 3D image. 

Each eye's glass contains a liquid crystal layer which has the property of becoming dark when voltage is applied, being otherwise transparent. The glasses are controlled by a timing signal that allows the glasses to alternately darken over one eye, and then the other, in synchronization with the refresh rate of the screen.

Contrary to glasses with a built in shutter system, Passive viewers filter constant streams of binocular input to the appropriate eye (just like how we see things normally) and rely on the brain to do the rest.

The two most common forms of passive viewer 3D systems are Anaglyph, and Polarization.

Remember going to the movies and getting all excited to see Spy Kids 3-D? I was even more excited when I received the DVD because 2 pairs of real life 3D glasses were included right there in the box!
Free 3D Glasses (with the purchase of the DVD)?? That's Amazing! 

The glasses I was so excited about used anaglyph technology and looked something like this:

Look familiar?

Anaglyph glasses work by encoding each eye's image using filters of different (usually chromatically opposite) colors, typically red and cyan. Anaglyph a3D images contain two differently filtered colored images, one for each eye. When viewed through the "color-coded" "anaglyph glasses", each of the two images reaches one eye, revealing an integrated stereoscopic image. The visual cortex of the brain fuses this into perception of a three dimensional scene or composition.

Despite the fact that anaglyph glasses are cheap and require no need for any special display-- they provide low quality of 3D and prevent the viewer from receiving accurate color information. 
These negatives are why most movie theaters have switched to the polarized 3D system.

Polarization Systems

Good 3D effect, cheaper, comfortable, requires a silver screen when using a projector, most commonly used type of 3D glasses

Polarization of light = the direction that a light wave travels (horizontally vs vertically vs circular)

To present stereoscopic pictures, two images are projected superimposed onto the same screen through polarizing filters or presented on a display with polarized filters. For projection, a silver screen is used so that polarization is preserved. The viewer wears low-cost eyeglasses which also contain a pair of opposite polarizing filters. As each filter only passes light which is similarly polarized and blocks the opposite polarized light, each eye only sees one of the images, and the effect is achieved.

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