Stereoscopic 3D – Producing the illusion of depth
It is natural to view objects in 3D. Photography and film use 2D to represent our 3D world and the first attempts to make stereoscopic 3D began in the form of anaglyph. The first method to produce anaglyph images was developed in 1853 by Wilhelm Rollmann in Germany. Generally two images from the perspective of the left and right eyes were projected or printed together as a single image. One side was processed through a red filter and the other side through a contrasting blue filter. And it is still used today but now it is done by using an image-processing computer program to simulate the effect of using color filters.
Viewing anaglyphs through colored glasses results in each eye viewing a slightly different picture. In red-blue anaglyph, the eye looking through the red filter sees the red parts of the image as white, and the blue parts as black; the eye covered by the blue filter gets the opposite effect. Actual black or white are perceived the same by each eye so that the viewer’s brain blends together the image it gets from each eye, and interprets the differences as being the result of varying depth.
3-D films have existed in some form since the 1950s even though they are more expensive to make than 2D and there is no industry-wide standard. 3D movies later became popular again beginning in the 1980s mostly because of the IMAX theaters and Disney theme parks. Mainstream 3-D films have became more successful recently, peaking with the runaway success of 3-D presentations of Avatar.
The very first PC games to use 3D were released in 1982 for the arcade – SubRoc and Vectrex 3D used a spinning disk method to create their 3D effect. Later, Sega and Nintendo brought out their proprietary 3D home console systems in the late 1980s that used active shutter glasses. And of course, the 1996 DoS PC game, Duke Nukem 3D mostly used the anaglyph glasses for the S3D effects.
James Cameron’s Avatar the Game uses multiple methods to achieve the S3D effects – anaglyph, 3D Vision active shutter glasses and HD3D over HDMI 1.4. The format “Frame Packing” (left and right image packed into one video frame with twice the normal bandwidth) is necessary for HDMI 1.4 3D devices. All three resolutions (720p50/60, and 1080p24) need to be supported by display devices, and at least one of them by playback devices. Other resolutions and formats are optional. HDMI 1.4 devices are capable of transmitting 3D pictures in full 1080p but HDMI 1.3 does not include this support. In addition, 3D images may be displayed at lower resolutions including interlaced or standard definition.
The advantages to an anaglyph 3D system is purely one of low cost – it is very cheap and Nvidia also gives you a way to sample S3D with anaglyph glasses for free – 3D Vision Discover – as long as you own a Nvidia graphics card. Unfortunately, this kind of 3D is dark and has definite issues with color transmission and reception.
Polarized glasses have the advantage of being relatively inexpensive – more expensive than the cheap throw-away anaglyph glasses but much cheaper than the active shutter glasses chosen by Nvidia. AMD calls their passive implementation of stereoscopic 3D, HD3D and polarized 3D glasses seem to be popular with them and their partners.
Polarized cuts the resolution in half horizontally because a passive S3D system takes one HD image and splits it in two. The result is that from an original 1080p image, each eye now sees a 540p image which is half of the combined resolution that an active system offers. Some feel that this loss of resolution results in less detailed images and a less pronounced 3D effect than the active shutter system.
The Active Shutter glasses
In 1999 Elsa’s 3D Revelator glasses came bundled with Elsa’s Erazor video cards and worked mostly with DirectX games. These glasses required a minimum 100Hz refresh rate using a CRT display. Once LCDs at 60 Hz became popular supplanting the CRT, the active technology Elsa used wouldn’t work any longer. The LCD’s refresh rate for each eye (half of 60Hz) is way too low for flicker-free gameplay and will cause eyestrain and headaches.