Uuglypher wrote:
Fotoartist,
“Shear” is “graphic art speak” used by some graphic/design artists for any free transformation used to suggest
an emphasis of, or change in perspective. ...
Note that it is simply ludicrous to claim that 3D image pairs with other than exclusively horizontal disparity offsets cannot fully support stereopsis with traditional viewing methods by the major part of the population). ....
You can't, of course, change the perspective (viewpoint) of an image by any form of distortion whether you use Shear or any other method. You can, as I showed in my first post, fake it so that it will appear to work with a simple scenario so long as you conform to the listed constraints.
All definitions of
Binocular vision come down to the unarguable fact that our eyes, being side-by-side, give us the ability to perceive a sensation of 3D because they receive information from two slightly separate viewpoints. As the article states, "
The overlapping of vision occurs due to the position of the eyes on the head (eyes are located on the front of the head, not on the sides). This overlap allows each eye to view objects with a slightly different viewpoint. As a result of this overlap of vision, binocular vision provides depth."
Can we see 3D in a properly prepared pair of images by free viewing?Most of us can do this but there are a couple of practical constraints:
1. Our eyes are about 2.5" (6.4 cm) apart. For parallel viewing, the center of the two images cannot be more than 2.5" apart because most of us cannot direct our eyes beyond a parallel gaze. That means that each image is limited to 2.5" in width.
2. For cross-eyed viewing, there is a limit to how closely we can view two images and cross our eyes to make them overlap. It becomes difficult to cross our eyes more than a normal reading distance of about 15 inches. The ratio of 15:2.5 is 6 so we can actually work with images larger than 2.5 inches in width if we back away from the display proportionately. For example, you might comfortably view a pair of 5 inch wide images from a distance of 30 inches with crossed eyes.
In either case, it takes some effort and possibly even some discomfort. It is difficult to sustain such a gaze for any length of time. It is even more difficult to examine the entire surface of the image while keeping our eyes locked in position.
Can we see 3D in a properly prepared pair of images via anaglyph or other presentation?All we need is the anaglyph glasses or some other visual aid to isolate the two images. There is no size restriction on the image (unless they are being viewed in a stereo viewer like a ViewMaster). We can then examine the entire surface of the image, corner to corner, with no discomfort.
But all of this assumes that the image pairs are
properly prepared - that they can actually be recognized as providing a 3D impression by either method. If you think that you can see 3D with free viewing but it fails when converted to anaglyph then
it has not been properly prepared.
You yourself have
admitted that 2D-3D conversion has its limits when it comes to distorting an image trying to do a conversion, "I have spent far more time than I care to admit trying to carry out 3D conversion..." If you really understood the issues you would not have even attempted it.