Stereograms require the use of a stereoscope for the 3D image to be seen.Īutostereograms, on the other hand, do not require a stereoscope. Read our affiliate disclosure here.Īutostereograms are two-dimensional (2D) images with repeating patterns that hide an underlying three-dimensional (3D) image. 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.This post may contain affiliate links. 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.
#Stereogram 3d 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 Most popular SIS images are generated to be viewed this way. 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). 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.
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