Anaglyph 3D

A stereo pair is a pair of images from slightly different perspectives at the same time. Objects closer to the camera(s) have greater differences in appearance and position within the image frames than objects further from the camera.

Historically cameras captured two color filtered images from the perspective of the left and right eyes which were projected or printed together as a single image, one side through a red filter and the other side through a contrasting color such as blue or green or mixed cyan. As outlined below, one may now, typically, use an image processing computer program to simulate the effect of using color filters, using as a source image a pair of either color or monochrome images. This is called mosaicking or image stitching.

In the 1970s filmmaker Stephen Gibson filmed direct anaglyph blaxploitation and adult movies. His "Deep Vision" system replaced the original camera lens with two color-filtered lenses focused on the same film frame.[7] In the 1980s, Gibson patented his mechanism.[8]

Many computer graphics programs provide the basic tools (typically layering and adjustments to individual color channels to filter colors) required to prepare anaglyphs from stereo pairs. In simple practice, the left eye image is filtered to remove blue & green. The right eye image is filtered to remove red. The two images are usually positioned in the compositing phase in close overlay registration (of the main subject). Plugins for some of these programs as well as programs dedicated to anaglyph preparation are available which automate the process and require the user to choose only a few basic settings.

There also exist methods for making anaglyphs using only one image, a process called stereo conversion. In one, individual elements of a picture are horizontally offset in one layer by differing amounts with elements offset further having greater apparent changes in depth (either forward or back depending on whether the offset is to the left or right). This produces images that tend to look like elements are flat standees arranged at various distances from the viewer similar to cartoon images in a View-Master.

A more sophisticated method involves use of a depth map (a false color image where color indicates distance, for example, a grayscale depth map could have lighter indicate an object closer to the viewer and darker indicate an object further away).[9] As for preparing anaglyphs from stereo pairs, stand-alone software and plug-ins for some graphics apps exist which automate production of anaglyphs (and stereograms) from a single image or from an image and its corresponding depth map.

As well as fully automatic methods of calculating depth maps (which may be more or less successful), depth maps can be drawn entirely by hand. Also developed are methods of producing depth maps from sparse or less accurate depth maps.[10] A sparse depth map is a depth map consisting of only a relatively few lines or areas which guides the production of the full depth map. Use of a sparse depth map can help overcome auto-generation limitations. For example, if a depth finding algorithm takes cues from image brightness an area of shadow in the foreground may be incorrectly assigned as background. This misassignment is overcome by assigning the shaded area a close value in the sparse depth map.

Paper anaglyph filters produce an acceptable image at low cost and are suitable for inclusion in magazines.

Piero della Francesca, Ideal City in an Anaglyph version 3D red cyan glasses are recommended to view this image correctly.

Complementary color anaglyphs employ one of a pair of complementary color filters for each eye. The most common color filters used are red and cyan. Employing tristimulus theory, the eye is sensitive to three primary colors, red, green, and blue. The red filter admits only red, while the cyan filter blocks red, passing blue and green (the combination of blue and green is perceived as cyan). If a paper viewer containing red and cyan filters is folded so that light passes through both, the image will appear black. Another recently introduced form employs blue and yellow filters. (Yellow is the color perceived when both red and green light passes through the filter.)

Anaglyph images have seen a recent resurgence because of the presentation of images on the Internet. Where traditionally, this has been a largely black & white format, recent digital camera and processing advances have brought very acceptable color images to the internet and DVD field. With the online availability of low cost paper glasses with improved red-cyan filters, and plastic framed glasses of increasing quality, the field of 3D imaging is growing quickly. Scientific images where depth perception is useful include, for instance, the presentation of complex multi-dimensional data sets and stereographic images of the surface of Mars. With the recent release of 3D DVDs, they are more commonly being used for entertainment. Anaglyph images are much easier to view than either parallel sighting or crossed eye stereograms, although these types do offer more bright and accurate color rendering, most particularly in the red component, which is commonly muted or desaturated with even the best color anaglyphs. A compensating technique, commonly known as Anachrome, uses a slightly more transparent cyan filter in the patented glasses associated with the technique. Processing reconfigures the typical anaglyph image to have less parallax to obtain a more useful image when viewed without filters.

Simple sheet or uncorrected molded glasses do not compensate for the 250 nanometer difference in the wavelengths of the red-cyan filters. With simple glasses the red filter image can be blurry when viewing a close computer screen or printed image since the retinal focus differs from the cyan filtered image, which dominates the eyes' focusing. Better quality molded plastic glasses employ a compensating differential diopter power to equalize the red filter focus shift relative to the cyan. The direct view focus on computer monitors has been recently improved by manufacturers providing secondary paired lenses, fitted and attached inside the red-cyan primary filters of some high-end anaglyph glasses. They are used where very high resolution is required, including science, stereo macros, and animation studio applications. They use carefully balanced cyan (blue-green) acrylic lenses, which pass a minute percentage of red to improve skin tone perception. Simple red/blue glasses work well with black and white, but the blue filter is unsuitable for human skin in color. U.S. Patent No. 6,561,646 was issued to the inventor in 2003. In the trade, the label "www.anachrome" is used to label diopter corrected 3D glasses covered by this patent.

(ACB) 'Anaglyphic Contrast Balance' is a patented anaglyphic production method by Studio 555.[13] Retinal Rivalry of color contrasts within the color channels of anaglyph images is addressed.

Contrasts and details from the stereo pair are maintained and re-presented for view within the anaglyph image. The (ACB) method of balancing the color contrasts within the stereo pair enables a stable view of contrast details, thus eliminating retinal rivalry. The process is available for red/cyan color channels but may use any of the opposing color channel combinations. As with all stereoscopic anaglyphic systems, screen or print, the display color should be RGB accurate and the viewing gels should match the color channels to prevent double imaging. The basic (ACB) method adjusts red, green and blue, but adjusting all six color primaries is preferred.

The effectiveness of the (ACB) process is proven with the inclusion of primary color charts within a stereo pair. A contrast-balanced view of the stereo pair and color charts is evident in the resulting (ACB) processed anaglyph image. The (ACB) process also enables black and white (monochromatic) anaglyphs with contrast balance.

Where full color to each eye is enabled via alternating color channels and color-alternating viewing filters, (ACB) prevents shimmer from pure-colored objects within the modulating image. Vertical and diagonal parallax is enabled with concurrent use of a horizontally oriented lenticular or parallax barrier screen. This enables a Quadrascopic full color holographic effect from a monitor.

ColorCode 3-D was deployed in the 2000s and uses amber and blue filters. It is intended to provide the perception of nearly full color viewing (particularly within the RG color space) with existing television and paint mediums. One eye (left, amber filter) receives the cross-spectrum color information and one eye (right, blue filter) sees a monochrome image designed to give the depth effect. The human brain ties both images together.

Images viewed without filters will tend to exhibit light-blue and yellow horizontal fringing. The backwards compatible 2D viewing experience for viewers not wearing glasses is improved, generally being better than previous red and green anaglyph imaging systems, and further improved by the use of digital post-processing to minimize fringing. The displayed hues and intensity can be subtly adjusted to further improve the perceived 2D image, with problems only generally found in the case of extreme blue.

The blue filter is centered around 450 nm and the amber filter lets in light at wavelengths at above 500 nm. Wide spectrum color is possible because the amber filter lets through light across most wavelengths in spectrum and even has a small leakage of the blue color spectrum. When presented the original left and right images are run through the ColorCode 3-D encoding process to generate one single ColorCode 3-D encoded image.

In the United Kingdom, television station Channel 4 commenced broadcasting a series of programs encoded using the system during the week of November 16, 2009.[14] Previously the system had been used in the United States for an "all 3-D advertisement" during the 2009 Super Bowl for SoBe, Monsters vs. Aliens animated movie and an advertisement for the Chuck television series in which the full episode the following night used the format.

Developed by TriOviz, Inficolor 3D is a patent pending stereoscopic system, first demonstrated at the International Broadcasting Convention in 2007 and deployed in 2010. It works with traditional 2D flat panels and HDTV sets and uses expensive glasses with complex color filters and dedicated image processing that allow natural color perception with a 3D experience. This is achieved through having the left image using the green channel only and the right using the red and blue channels with some added post processing, which the brain then combines the two images to produce a nearly full color experience. When observed without glasses, some slight doubling can be noticed in the background of the action which allows watching the movie or the video game in 2D without the glasses. This is not possible with traditional brute force anaglyphic systems.[15]

Inficolor 3D is a part of TriOviz for Games Technology, developed in partnership with TriOviz Labs and Darkworks Studio. It works with Sony PlayStation 3 (Official PlayStation 3 Tools & Middleware Licensee Program)[16] and Microsoft Xbox 360 consoles as well as PC.[17][18] TriOviz for Games Technology was showcased at Electronic Entertainment Expo 2010 by Mark Rein (vice-president of Epic Games) as a 3D tech demo running on an Xbox 360 with Gears of War 2.[19] In October 2010 this technology has been officially integrated in Unreal Engine 3,[17][18] the computer game engine developed by Epic Games.

Stereo 3D visualization video of the surface of a human brain 3D red cyan glasses are recommended to view this image correctly.

Video games equipped with TriOviz for Games Technology are: Batman Arkham Asylum: Game of the Year Edition for PS3 and Xbox 360 (March 2010),[20][21][22] Enslaved: Odyssey to the West + DLC Pigsy's Perfect 10 for PS3 and Xbox 360 (Nov. 2010),[23][24] Thor: God of Thunder for PS3 and Xbox 360 (May 2011), Green Lantern: Rise of the Manhunters for PS3 and Xbox 360 (June 2011), Captain America: Super Soldier for PS3 and Xbox 360 (July 2011). Gears of War 3 for Xbox 360 (September 2011), Batman: Arkham City for PS3 and Xbox 360 (October 2011), Assassin's Creed: Revelations for PS3 and Xbox 360 (November 2011), and Assassin's Creed III for Wii U (November 2012). The first DVD/Blu-ray including Inficolor 3D Tech is: Battle for Terra 3D (published in France by Pathé & Studio 37 - 2010).

Anachrome glasses

Full color Anachrome red (left eye) and cyan (right eye) filters 3D anachrome glasses are recommended to view this image correctly.

A variation on the anaglyph technique from the early 2000s is called "Anachrome method". This approach is an attempt to provide images that look nearly normal, without glasses, for small images, either 2D or 3D, with most of the negative qualities being masked innately by the small display. Being "compatible" for small size posting in conventional websites or magazines. Usually a larger file can be selected that will fully present the 3D with the dramatic definition. The 3D (Z axis) depth effect is generally more subtle than simple anaglyph images, which are usually made from wider spaced stereo pairs. Anachrome images are shot with a typically narrower stereo base, (the distance between the camera lenses). Pains are taken to adjust for a better overlay fit of the two images, which are layered one on top of another. Only a few pixels of non-registration give the depth cues. The range of color perceived, is noticeably wider in Anachrome image, when viewed with the intended filters. This is due to the deliberate passage of a small (1 to 2%) of the red information through the cyan filter. Warmer tones can be boosted, because each eye sees some color reference to red. The brain responds in the mental blending process and usual perception. It is claimed to provide warmer and more complex perceived skin tones and vividness.

Interference principle

This technique uses specific wavelengths of red, green, and blue for the right eye, and different wavelengths of red, green, and blue for the left eye. Eyeglasses which filter out the very specific wavelengths allow the wearer to see a full color 3D image. Special interference filters (dichromatic filters) in the glasses and in the projector form the main item of technology and have given the system this name. It is also known as spectral comb filtering or wavelength multiplex visualization. Sometimes this technique is described as a "super-anaglyph" because it is an advanced form of spectral-multiplexing which is at the heart of the conventional anaglyph technique. This technology eliminates the expensive silver screens required for polarized systems such as RealD, which is the most common 3D display system in theaters. It does, however, require much more expensive glasses than the polarized systems.

Dolby 3D uses this principle. The filters divide the visible color spectrum into six narrow bands – two in the red region, two in the green region, and two in the blue region (called R1, R2, G1, G2, B1 and B2 for purposes of this description). The R1, G1 and B1 bands are used for one eye image, and R2, G2, B2 for the other eye. The human eye is largely insensitive to such fine spectral differences so this technique is able to generate full-color 3D images with only slight color differences between the two eyes.[25]

The Omega 3D/Panavision 3D system also used this technology, though with a wider spectrum and more "teeth" to the "comb" (5 for each eye in the Omega/Panavision system). The use of more spectral bands per eye eliminates the need to color process the image, required by the Dolby system. Evenly dividing the visible spectrum between the eyes gives the viewer a more relaxed "feel" as the light energy and color balance is nearly 50-50. Like the Dolby system, the Omega system can be used with white or silver screens. But it can be used with either film or digital projectors, unlike the Dolby filters that are only used on a digital system with a color correcting processor provided by Dolby. The Omega/Panavision system also claims that their glasses are cheaper to manufacture than those used by Dolby.[26] In June 2012 the Omega 3D/Panavision 3D system was discontinued by DPVO Theatrical, who marketed it on behalf of Panavision, citing "challenging global economic and 3D market conditions".[27] Although DPVO dissolved its business operations, Omega Optical continues promoting and selling 3D systems to non-theatrical markets. Omega Optical's 3D system contains projection filters and 3D glasses. In addition to the passive stereoscopic 3D system, Omega Optical has produced enhanced anaglyph 3D glasses. The Omega's red/cyan anaglyph glasses use complex metal oxide thin film coatings and high quality annealed glass optics.

Simple paper uncorrected gel glasses, cannot compensate for the 250 nanometer difference in the wavelengths of the red-cyan filters. With simple glasses, the red filtered image is somewhat blurry, when viewing a close computer screen or printed image. The red retinal focus differs from the image through the cyan filter, which dominates the eyes' focusing. Better-quality molded acrylic glasses frequently employ a compensating differential diopter power (a spherical correction) to balance the red filter focus shift relative to the cyan, which reduces the innate softness and diffraction of red filtered light. Low-power reading glasses worn along with the paper glasses also sharpen the image noticeably.

The correction is only about 1/2 + diopter on the red lens. However, some people with corrective glasses are bothered by difference in lens diopters, as one image is a slightly larger magnification than the other. Though endorsed by many 3D websites, the diopter "fix" effect is still somewhat controversial. Some, especially the nearsighted, find it uncomfortable. There is about a 400% improvement in acuity with a molded diopter filter, and a noticeable improvement of contrast and blackness. The American Amblyopia Foundation uses this feature in their plastic glasses for school screening of children's vision, judging the greater clarity as a significant plus factor.

Plastic glasses, developed in recent years, provide both the diopter "fix" noted above, and a change in the cyan filter. The formula provides intentional "leakage" of a minimal (2%) percentage of red light with the conventional range of the filter. This assigns two-eyed "redness cues" to objects and details, such as lip color and red clothing, that are fused in the brain. Care must be taken, however, to closely overlay the red areas into near-perfect registration, or "ghosting" can occur. Anachrome formula lenses work well with black and white, but can provide excellent results when the glasses are used with conforming "anachrome friendly" images. The US Geological Survey has thousands of these "conforming" full-color images, which depict the geology and scenic features of the U.S. National Park system. By convention, anachrome images try to avoid excess separation of the cameras and parallax, thereby reducing the ghosting that the extra color bandwidth introduces to the images.

Image as originally presented by NASA with foreground spilling from the frame. This is a two-color (red-cyan) anaglyph from the Mars Pathfinder mission. To view, use a red filter for the left eye and a cyan filter for the right eye. Note that the distant mountain images are aligned, placing them at the screen, and the confusing appearance in the lower right corner. 3D red cyan glasses are recommended to view this image correctly.

Image adjusted so that most objects appear to be beyond the frame. Note that the mountain images are now separated when viewed without the glasses. This follows the rule for a red left eye filter when distant objects are beyond the image plane: RRR-Red to Right Receding for dark objects on lighter background in the image as it appears without wearing the filters. 3D red cyan glasses are recommended to view this image correctly.

The adjustment suggested in this section is applicable to any type of stereogram but is particularly appropriate when anaglyphed images are to be viewed on a computer screen or on printed matter.

Those portions of the left and right images that are coincident will appear to be at the surface of the screen. Depending upon the subject matter and the composition of the image it may be appropriate to make this align to something slightly behind the nearest point of the principal subject (as when imaging a portrait). This will cause the near points of the subject to "pop out" from the screen. For best effect, any portions of a figure to be imaged forward of the screen surface should not intercept the image boundary, as this can lead to a discomforting "amputated" appearance. It is of course possible to create a three-dimensional "pop out" frame surrounding the subject in order to avoid this condition.

If the subject matter is a landscape, you may consider putting the frontmost object at or slightly behind the surface of the screen. This will cause the subject to be framed by the window boundary and recede into the distance. Once the adjustment is made, trim the picture to contain only the portions containing both left and right images. In the example shown above, the upper image appears (in a visually disruptive manner) to spill out from the screen, with the distant mountains appearing at the surface of the screen. In the lower modification of this image the red channel has been translated horizontally to bring the images of the nearest rocks into coincidence (and thus appearing at the surface of the screen) and the distant mountains now appear to recede into the image. This latter adjusted image appears more natural, appearing as a view through a window onto the landscape.

Since the advent of the Internet, a variant technique has developed where the images are specially processed to minimize visible mis-registration of the two layers. This technique is known by various names, the most common, associated with diopter glasses, and warmer skin tones, is Anachrome. The technique allows most images to be used as large thumbnails, while the 3D information is encoded into the image with less parallax than conventional anaglyphs.

Disney Studios released Hannah Montana & Miley Cyrus: Best of Both Worlds Concert in August 2008, its first anaglyph 3D Blu-ray Disc. This was shown on the Disney Channel with red-cyan paper glasses in July 2008.

However, on Blu-ray Disc anaglyph techniques have more recently been supplanted by the Blu-ray 3D format, which uses Multiview Video Coding (MVC) to encode full stereoscopic images. Though Blu-ray 3D does not require a specific display method, and some Blu-ray 3D software players (such as Arcsoft TotalMedia Theatre) are capable of anaglyphic playback, most Blu-ray 3D players are connected via HDMI 1.4 to 3D televisions and other 3D displays using more advanced stereoscopic display methods, such as alternate-frame sequencing (with active shutter glasses) or FPR polarization (with the same passive glasses as RealD theatrical 3D).

These techniques have been used to produce 3-dimensional comic books, mostly during the early 1950s, using carefully constructed line drawings printed in colors appropriate to the filter glasses provided. The material presented were from a wide variety of genres, including war, horror, crime, and superhero. Anaglyphed comics were far more difficult to produce than normal comics, requiring each panel to be drawn multiple times on layers of acetate. While the first 3D comic in 1953 sold over two million copies, by the end of the year sales had bottomed out, though 3D comics have continued to be released irregularly up until the present day.[37]

The single valued function of two variables ${\displaystyle z(x,y)=x^{2}+y^{3}}$ with the function value displayed as the height

Anaglyph by the Mars Reconnaissance Orbiter's HiRISE camera highlighting Martian lava terrain that looks like an elephant

Anaglyph image of the protein DHFR

3D red cyan glasses are recommended to view this image correctly.

Three-dimensional display can also be used to display scientific data sets, or to illustrate mathematical functions. Anaglyph images are suitable both for paper presentation, and moving video display (see neuroimage related paper[38]). They can easily be included in science books, and viewed with cheap anaglyph glasses.

Anaglyphy (including, among others, aerial, telescopic, and microscopic images) is being applied to scientific research, popular science, and higher education.[39]

Also, chemical structures, particularly for large systems, can be difficult to represent in two dimensions without omitting geometric information. Therefore, most chemistry computer software can output anaglyph images, and some chemistry textbooks include them.

Today, there are more advanced solutions for 3D imaging available, like shutter glasses together with fast monitors. These solutions are already extensively used in science. Still, anaglyph images provide a cheap and comfortable way to view scientific visualizations.