Editing Autostereogram (section)

{{Short description|Visual illusion of 3D scene}}
[[Image:Stereogram Tut Random Dot Shark.png|thumb|300px|A random dot autostereogram encoding a 3D scene of a shark, which can be seen with proper viewing technique. ([[Image:Stereogram guide parallel.png|10px]]) {{See below|{{section link||Viewing techniques}}, below}}]]
{{multiple image
 | width = 100
 | image1 = Autostereogram normal vergence.svg
 | caption1 = Aligned [[vergence]] and [[accommodation (eye)|ac&shy;com&shy;mo&shy;da&shy;tion]]. How one usually views objects.<ref name="Invitation">Stephen M. Kosslyn, Daniel N. Osherson (1995). ''An Invitation to Cognitive Science, 2nd Edition - Vol. 2: Visual Cognition'', p. 65 fig. 1.49. {{ISBN|978-0-262-15042-2}}.</ref>
 | image2 = Autostereogram cross-eyed vergence.svg
 | caption2 = Cross-eyed vergence<!--"vergence" is a real word spelled correctly--> {{Stereogram|cross}}.<ref name="Invitation"/> Arrow indicates ac&shy;com&shy;mo&shy;da&shy;tion.
 | image3 = Autostereogram wall-eyed vergence.svg
 | caption3 = Wall-eyed ("parallel") convergence {{Stereogram|wall}}.<ref name="Invitation"/>
 | footer = 
}}
[[File:Autostereogram cross- and wall- eyed vergence example.svg|275px|thumb|The top and bottom images produce a dent or projection depending on whether viewed with cross- {{stereogram|cross}} or wall- {{stereogram|wall}} eyed vergence.]]
[[File:Autostereogram of a cube rotating. You will need to learn how to see an autostereogram to see this..gif|thumb|Autostereogram of a cube rotating]]
[[File:Autostereogram 3d effect..jpg|thumb|Autostereogram]]
An '''autostereogram''' is a [[Two-dimensional Euclidean space|two-dimensional (2D)]] image that can create the optical illusion of a [[Three-dimensional space|three-dimensional (3D)]] scene. Autostereograms use only one image to accomplish the effect while normal [[stereogram]]s require two. The 3D scene in an autostereogram is often unrecognizable until it is viewed properly, unlike typical stereograms. Viewing any kind of stereogram properly may cause the viewer to experience [[vergence-accommodation conflict]].

The optical illusion of an autostereogram is one of [[depth perception]] and involves [[stereopsis]]: depth perception arising from the different perspective each eye has of a three-dimensional scene, called binocular [[parallax]].

Individuals with disordered binocular vision and who cannot perceive depth may require a wiggle stereogram to achieve a similar effect.

The simplest type of autostereogram consists of a horizontally repeating pattern, with small changes throughout, that looks like [[wallpaper]]. When viewed with proper [[vergence]], the repeating patterns appear to float above or below the background. The well-known ''[[Magic Eye]]'' books feature another type of autostereogram called a random-dot autostereogram {{See below|{{section link||Random-dot}}, below}}, similar to the first example, above. In this type of autostereogram, every [[pixel]] in the image is computed from a pattern strip and a [[depth map]]. A hidden 3D scene emerges when the image is viewed with the correct vergence.

Unlike normal stereograms, autostereograms do not require the use of a [[stereoscope]]. A stereoscope presents 2D images of the same object from slightly different angles to the left eye and the right eye, allowing the viewer to reconstruct the original object via [[binocular disparity]]. When viewed with the proper vergence<!--"vergence" is a real word spelled correctly-->, an autostereogram does the same, the binocular disparity existing in adjacent parts of the repeating 2D patterns.

There are two ways an autostereogram can be viewed: ''wall-eyed'' and ''cross-eyed''.{{efn|name=strabismus}} Most autostereograms (including those in this article) are designed to be viewed in only one way, which is usually wall-eyed. Wall-eyed viewing requires that the two eyes adopt a relatively [[parallel (geometry)|parallel]] angle, while cross-eyed viewing requires a relatively [[convergence (eye)|convergent]] angle. An image designed for wall-eyed viewing if viewed correctly will appear to pop out of the background, whereas if viewed cross-eyed it will instead appear as a cut-out behind the background and may be difficult to bring entirely into focus.{{efn|name=Vice versa|If a two-image stereogram, wallpaper, or random-dot autostereogram designed for wall-eyed viewing is viewed cross-eyed, or vice versa, all details on the ''z''-axis will be reversed – objects that were meant to be seen to rise above the background will appear to sink into it. However, there may be some incoherence due to overlapping (an object originally intended to project in front of another object will now project behind it). For example, the black lines in [[:File:Stereogram Tut Simple.png]].}}