DISPLAYING 3D IMAGES - ALGORITHMS FOR SINGLE-IMAGE RANDOM-DOT STEREOGRAMS

Stereopsis, the fusing of two separate images, one for each eye, to pr oduce the effect of depth is natural when viewing solid objects. The e ffect can also be produced with two-dimensional pictures if each eye r eceives a separate image corresponding to the view it would have of th e actual 3D object. This article describes how to generate a single im age that when viewed in the appropriate way on paper or on an ordinary computer screen appears to the brain as a 3D scene. The image is a st ereogram composed of seemingly random dots. The authors present a new, simple, and symmetric algorithm for generating such images from a sol id model, along with the design parameters and their influence on the display. The algorithm improves on previously described algorithms in several ways: It is symmetric and hence free from directional (right-t o-left or left-to-right) bias, it corrects a slight distortion in the rendering of depth, it removes hidden parts of surfaces, and it elimin ates a type of artifact known as an ''echo.'' Random-dot stereograms a re typically difficult to view initially because viewers must alter th eir eyes' convergence. If a computer screen is used for output rather than paper, the problem can be ameliorated by shimmering, or time-mult iplexing of pixel values. Example stereograms art included, with detai led instructions for viewing. The authors also describe a simple compu tational technique for determining what is present in a stereogram so that if viewing is difficult, a viewer can determine what to look for.