Make Mine a Double How to Create Stereoscopic Images with Bryce STEREO PAIRS and freeviewing 3d images The picture for this tutorial is called Ice Pond, and is presented on this page as a "stereo pair" image. This is a scene modelled and raytraced in Bryce, and you can perceive it fully in three dimensions if you "free-view" the pair. If you remember and participated in the random dot stereogram (magic eye) poster craze of the eighties, you'll have little trouble learning to free-view stereo pairs. Let's start with learning this. It takes only a few minutes, and will make the rest of the tutorial much more interesting - plus, you'll get to stretch and exercise some muscles. Put the magazine down on a flat, stable surface that will allow you to view the Ice Pond images well illuminated but without glare. The two images are printed 2.3 inches apart on the page. This is about the separation between your pupils. Thus, when you get down right on top of the image pair (with your nose literally touching the little white space between the images), and you look straight ahead (through the page), the images will appear "fused" (they appear as one image, not as a pair), though of course dreadfully out of focus. Ignore the blurriness, and concentrate on the fused image. Slowly, s l o w l y move your head away from the page, while continuing to stare through the image pair. Your brain will try to focus on the page, but then the pair will snap out of fusion. Try again, and stay relaxed. As you move farther from the page, the fused pair will look like three images - the center image is the fused 3d image, and that is where you will ultimately see depth. Stop your mind's eye from focussing on the page by staying relaxed and concentrating on the blurry, out of focus features in the fused image. After a while, your mind will automatically focus the eyes on the fused image without focussing on the page. Then you will perceive the depth in the picture! STEREO VISION Now, why was that so difficult? And how can there be depth perceived when the pair of images is viewed in this odd manner? What you were fighting is a physiological link between accomodation, the actual optical focus of each eye, and convergence, the physical pointing of the eyes, as they triangulate inwards for nearby objects. The brain is not used to focussing the eyes for close-up, when the eyes are "pointed" far away (i.e. pointed parallel, as at infinity). Yet this is exactly what you achieve when you free-view such stereo pairs. The perception of depth comes from subtle differences between the left and right images. Although both are renderings of the same scene, they are made from two slightly different viewpoints (camera positions) - just as your two eyes give your mind two images of the world around you taken from two different viewpoints. The differences between the two images are all in the apparent relative horizontal positions of different objects in the scene. For example, looking at the left and right image, notice how the horizontal position of the larger fish shifts relative to the round leaf floating above it. It is this relative shift, this apparent disparity, that the mind's eye interprets as depth in the fused image. Continue to Bryce Model.

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