# Glasses-enabled 3D

This is a section that feels a little tangential to displays, but also feels weird if it isn't included. There are several methods of viewing images that involve wearing special glasses like the classic red/cyan or red/green anaglyph glasses. The color versions work by displaying either multiple colors filtering one part of a stereo image to each eye resulting in the sensation of stereo vision. Polarized glasses also allow a similar effect and can be used with either passive or active polarization methods. Most of the glasses enabled effects are:

* Anaglyph Glasses
  * This requires the display of an image in both red/cyan (or sometimes red and green). The glasses then filter each of those to each eye, resulting in an image that feels 3D. It certainly has its use cases, but most of its disadvantages are inability to maintain proper color for the rest of the content.
* Chromadepth glasses
  * These essentially work by bringing red to the foreground and sorting other colors to the background between the two stereo sides.
  * [See some for sale here](https://www.3dglassesonline.com/products/chromadepth/)
* Diffraction Glasses
  * These aren't for 3D, but worth mentioning - they are mostly for things like viewing fireworks and other shapes show up overtop of things like holiday lights and candles.
* Active Polarization
  * These work by synchronizing their shutter with a polarized projection source that rapidly switches the polarization per frame, as well as tells the active glasses to use fast switching LCD to cover each eye. 
  * Since the screen is projecting a full image for each frame being shown to each eye, active polarization does not cause a loss in spatial resolution like passive polarization does.
* Passive Polarization
  * This is similar to the above, but does not require a sychronized polarizer, but it does require a retroreflective screen that can maintain polarization.
  * The main advantage to this method is that the glasses are significantly cheaper.


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