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3D imaging is a process to render a three-dimensional image on a two-dimensional surface by creating the optical illusion of depth. Generally, 3D imaging uses two still or motion camera lenses a slight distance apart to photograph a three-dimensional object. The process effectively duplicates the stereoscopic vision of human eyes. The image is reproduced as two flat images that viewers’ eyes see separately, creating a visual illusion of depth as their brains combine the images into a single one.
The spot where the left and right images overlap is the point of convergence. This point is generally the subject of the image as it is the clearest part of the image. Objects at the point of the convergence appear to exist on the surface screen. As objects in 3D imaging move further from the point of convergence, they appear either closer or further away from the viewer, creating the illusion of depth.
3D imaging is produced either as two separate images viewed side by side or as a single image with two overlapping elements. In stereoscopy, two static photographs are placed side by side and the viewer looks at the left and right images with each eye separately. Stereo photography dates back to early development of photography. This is a simpler process of 3D imagery only requiring two still cameras to produce two static images. These images also can be viewed by each eye independently without the aid of optical equipment.
A stereoscope is a device that holds the stereoscopic images on a single card or projects them the appropriate distance for the viewer to see the images in three dimensions. To see the image in three dimensions without a stereoscope, the viewer can look at both side-by-side images and cross his or her eyes until the images merge. In the combined overlapping, three images appear, the middle of which appears in three dimensions.
Single 3D images such as those used in 3D movies, are projected on a screen and are usually viewed with specialized optical equipment like 3D glasses or polarized lenses that split the two images for each eye. With the naked eye, these images appear like a double exposure. Early 3D movies used red and cyan filters. The 3D glasses contained red and cyan lenses, removing image produced by the other filter creating a separate image for each eye.
Modern 3D imaging instead splits the image with aid of polarized lenses. The process is essentially the same but does not distort the colors of the image like red and cyan filters do. Software programs create 3D imagery with various techniques to create the illusion of motion, by moving objects closer to the view more than those further away.