See also Cyclopean perception, stereopsis, visual illusion. It is constructed by generating two arrays of randomly placed dots, identical except for a clearly defined region that is slightly shifted sideways in one of the arrays, and it is usually presented for viewing by printing one of the arrays in red and the other in green or cyan (blue-green), with a slight horizontal displacement so that the unshifted dots do not fall exactly on top of one another, and it is viewed with spectacles having one red and one green or cyan lens. We then subdivide the depth map, shown in Figure 41-8, into four strips ( num_strips) and divide the result map into five strips ( num_strips + 1), because we need a reference strip to start with.A type of anaglyph for studying binocular depth perception invented by the Hungarian-born US radar engineer and psychologist Bela Julesz (1928–2003) at Bell Telephone Laboratories in 1960, consisting of two random arrays of dots that when viewed stereoscopically, one array being viewed by each eye, appears to contain a form such as a triangle or square lying in a plane either in front or behind the rest of the dots, bounded by an illusory contour. To simplify this example, we use four strips ( num_strips = 4), but for a true SIS we would use more. To render the SIS, we start by subdividing the depth map and the result image into vertical strips. Invert depth: Boolean value indicating whether depth values should be inverted (1 – depth).
STEREOGRAM NUDES FULL
Depth factor: Floating-point value in the range 0.0 to 1.0, with 1.0 meaning full depth.Number of strips ( num_strips): Integer value, usually from 8 to 24.When creating a new SIS, we need to consider parameters: the number of strips to use the depth factor, which can increase or decrease the depth perception (which in turn controls the amount of deformation applied to the pattern tiles) and whether to invert the depth values (white can be considered depth 0 or full-depth 1). 41.2 Creating a Single-Image StereogramĪn SIS is generated from a given depth map (that is, a grayscale image with depth information) and a tile pattern (usually a colored tile image), as in Figure 41-6.įigure 41-7 The Resulting Stereogram 41.2.1 Parameters We call it Mapped Texture Stereogram (MTS). Most popular SIS images are generated to be viewed this way. This stereogram image I created in 2007 uses a special technique of aligning 2D texture elements with the hidden object, giving it details. Viewers can cross their eyes behind the image plane, thereby inverting their depth perception but still resulting in a 3D image.
But in an SIS, because the separation between the strips is smaller than the distance between our eyes, there is an alternative, more comfortable way to view the image. With stereo photography and classic RDS images, viewers must always cross their eyes in front of the image plane. Actually, an RDS pair works just like an SIS with two strips.
These differences allow the perception of depth.įigure 41-5 Viewing a Stereogram with Four Stripsįor an RDS, the eye crossing point must be farther in front of the image plane (that is, closer to the viewer) than in an SIS, so that the displacement of the images seen is the size of the image itself.
Our eyes are separated from each other by about 65 mm, and this disparity causes slightly different images to be presented to the brain. The idea behind stereo photography is to take two similar photographs, but from different positions displaced horizontally (like our eyes). Stereo photography is very old, dating back to 1838, but some of the old stereo cameras and stereo photograph viewers, such as the one shown in Figure 41-1a, can still be found at antique shops. Stereograms evolved from stereo photography, in which two photographs are taken from slightly different camera positions (representing the displacement between our eyes). It all started back in the 1960s, when Bela Julesz, who worked at (AT&T) Bell Labs researching human vision-particularly depth perception and pattern recognition-created the random-dot stereogram (RDS). About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features Press Copyright Contact us Creators. 41.1 What Is a Stereogram?Ī stereogram is a 2D image that encodes stereo information so that, when viewed correctly, it reveals a hidden 3D scene. The CD content, including demos and content, is available on the web and for download. Shop affordable wall art to hang in dorms, bedrooms, offices, or anywhere blank walls arent. Some stereograms are used only to explore fusion. You can purchase a beautifully printed version of this book, and others in the series, at a 30% discount courtesy of InformIT and Addison-Wesley. Unique Stereogram Posters designed and sold by artists. stereogram Paired similar photographs or drawings which when viewed in a stereoscope give the sensation of stereopsis.
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