Abstract
Georgeson 1979 described an ingenious method for producing a random-dot anaglyph of any 3D object, by projecting dots on the object and viewing directly with both eyes or in an anaglyph. He reported that a random-dot stereoscopic hollow face does not give the illusion of convexity — which is normally observed as a powerful effect — instead, a strong percept of a hollow face is seen binocularly. We have replicated his findings. In practice projecting the dots illuminates the face, revealing monocular face features; so as well as projecting dots, which give unwanted monocular cues, we painted luminous spots on black face masks to minimize the general illumination of their surfaces. In another experiment, we added spots on visible face masks, for both monocular and binocular viewing. These spots greatly reduce the strength of the binocular illusion, but do not appreciably affect the monocular illusion. The spots are captured by the surface of the face, however it is seen. The fact that the binocular illusion is more affected by the dots than the monocular illusion, suggests that the role of the dots is to strengthen the binocular cues rather than mask the features of the face. Georgeson M A (1979) Random-dot stereograms of real objects: Observations on stereo faces and moulds. Perception 8 585–588