P3D RE: stereo x-rays of sea shells

[abram klooswyk <abram.klooswyk@xxxxxx>]

Peter Abrahams (P3D Digest 3667, 15 Jan 2000):
>I have my stereo radiographs of sea shells as image files,
>posted to the web.

Very nice stereo X-rays Peter!

With three instances of a graphics viewer *) I have
placed the "Epitonm" in L - R - L format on my screen, so with
crossed-eyes freeviewing I see the pseudoscopic and the
orthoscopic version side by side.

Pseudoscopic viewing of X-rays doesn't give local disturbing
effects, as is the rule in pseudo viewing of most natural
scene stereo images, the depth conversion is complete.
So 'pseudoscopic' has a different meaning with X-rays, for,
although transposition gives depth inversion, you can only
identify the right direction (orthoscopic viewing) by studying
the details of image content, the anatomy, for clues.

In this case the spiral direction of the shell winding is
_opposite_ in both ways of viewing (which follows from geometry).
Is it true that almost all spiral shells have right-handed screw
windings (as most common hardware screws and bolts)?
Then the "epitonm" is either an exception, or the L and R images
(epitonml.jpg and epitonmr.jpg) and have been interchanged!

Abram Klooswyk

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*) Irfanview, a freeware Windows viewer, zip-file 459 kB at:
http://stud1.tuwien.ac.at/~e9227474/
1. start first copy of IrfanView
2. activate multiple instances
    [Options > Properties > Others 1, Uncheck (= no V before):
     "Only 1 instance of IrfanView is active"]
3. start next two copies of Irfanview
4. load an image (file, open) in each copy
5. diminish the screen images (by pressing the - key a few times)
6. move the windows on the screen to align the images.
(The new IrfanView versions also make HTML Thumbnail pages)
=========