The world we see has three dimensions: height, width, and depth. However, while watching a movie, our eyes could only see two of these dimensions; that is, until 3D technology revolutionized the shape of modern movies. Yet, the movie industry is determined not to stop at just that.
Recently, 3D propaganda is everywhere; people already want to see and try something new. This technology, together with the revolutionary motion and control experiences, is already giving big hints of things to come in the world of gaming and entertainment.
People with normal eyesight have something called stereoscopic vision. The 6‑cm gap between our eyes means that each one sees the world from a slightly different point of view. Rather than perceiving a confusing double vision, our brains process the differences between the two images to create a mental model of the 3D space. This is called stereopsis.
A 3D movie or an S3D—stereoscopic 3D—movie is a motion picture that augments the illusion of depth perception. A regular motion picture camera system is used to record the images as seen from left and right eye perspective or computer-generated imagery generates the two perspectives in post-production. Different left and right eye images are recorded/generated because our left eye sees differently than the right one. Due to this difference, we get impressions of depth, and same principle is used to generate 3D images and films.
The theory behind 3D visuals is fairly simple; however, it is not so easy in practice. First, you need two discrete images that interact in a meaningful way to create a 3D effect. Then, you need a system that sends each image to the correct eye and that eye only; special projection hardware and/or eyewear are used to provide the illusion of depth when viewing the film.
Over the years, cinemas have experimented with 3D technology, applying various techniques. Anaglyph images were the earliest method of presenting theatrical 3D technology. The films had two different layers with two different colors, typically red and green; these two layers were superimposed in a way to counterbalance each other.
The audience were given 3D glasses with red and blue filters where the red part of the image was obstructed by the green lens and vice versa. This ensured that the viewers’ right and left eyes formed two different images and hence the optical illusion of depth was created.
The downside is that the picture is in monochrome, and not even a simple grayscale; the color filtering by the lenses thus distorted the final color. The fact that each eye sees different colors is distracting; many among the audience watching a 3D film complained of headaches and nausea. Full-colored anaglyph techniques have been developed, but in truth they are only partly full-color and partly 3D.
Another technique that has been applied in cinemas is the battery-powered glasses that use LCD shutters to block the light to each eye in turn. The timing of the alternating lenses was synchronized with frames on the screen; when the projector flashed up a frame for the left eye followed by a frame for the right eye, only the correct eye saw each image.
This gave a full-color 3D image and a convincing 3D effect, but the alternating shutters could be distracting. They were not comfortable to wear either, resembling a futuristic welder’s mask. As the technology was built into the glasses, it was expensive to equip each person in the theater, so it is not surprising that this approach never caught on in cinemas.
In case of polarization systems, to present a stereoscopic motion picture, two images are projected superimposed onto the same screen through different polarizing filters. The viewer wears low-cost eyeglasses that contain a pair of polarizing filters oriented differently (clockwise/counterclockwise with circular polarization or at 90 degree angles, usually 45 degrees and 135 degrees with linear polarization).
Each filter passes only the light similarly polarized and blocks the light polarized differently; each eye sees a different image. This is used to produce a three-dimensional effect by projecting the same scene into both eyes, but depicted from slightly different perspectives.
Since no head tracking is involved, the entire audience can view the stereoscopic images at the same time. Additionally, since both lenses have the same color, people with one dominant eye (amblyopia), where one eye is used more, are able to see the 3D effect, previously negated by the separation of the two colors.
Circular polarization has an advantage over linear polarization in that the viewer does not need to have their head upright and aligned with the screen for the polarization to work properly.
With linear polarization, turning the glasses sideways causes the filters to go out of alignment with the screen filters, causing the image to fade and for each eye to see the opposite frame more easily.
For circular polarization, the polarizing effect works regardless of how the viewer’s head is aligned with the screen such as tilted sideways, or even upside down. The left eye will still only see the image intended for it, and vice versa, without fading.
With the progress of 3D technology, 3D viewing has been able to reach exceptional heights with the help of purposely made animation movies for 4D and 5D theaters; 4D and 5D being marketing terms, not actual geometrical dimensions.
Recently, 3D viewing has been accompanied with synchronization of some special effects installed in the theaters. For example, when it rains in the movie, the audience also experiences the same; when it is lightening in the movie, the same happens in the theater. Other effects also include wind, fog, smell, sensation, etc.
In 5D theaters, seats move in synchronization with motion in the movie, thus providing immersive experience to the audiences. To do this at least six-directional seat movement is required: Left-Right tilts; Forward-Backward Tilts and Up-Down movements. These theaters show an excellent integration of 3D technology, audio, motion synchronization, and multiple special effects using specialized software.
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Nowadays, people might hear the terms 6D or 7D―again, not referring to actual geometrical dimensions―however, thus far, it seems that they are simply a marketing myth. The fact remains that there are only 3 geometrical dimensions; having already added sound and motion effects to visual ones, what could be next for the motion picture industry?
References
http://modern5d.com/3d-movies-work
news.discovery.com
www.visionnw.com
www.rsacosmos.com
www.expertreviews.co.uk
computer.howstuffworks.com