RAY 3D's cross-eye training target

[P3D Norm Goldblatt <normgold@xxxxxxxxxx>]

I was looking at Ray Hannigan's targets (a cross and a circle) for
training the eyes for cross-eye stereoviewing and noticed how
difficult it was to keep the cross and circle centered. The two
images would swim and then depart!  Excedrin Headache 3(D)!
A bit discouraging. The lack of anything to 'fuse' and
thus anchor the convergence seems to be the problem. 
Using two vertical lines the brain SNAPS the 'foursome' into a
stable threesome and stays there.  Much more gratifying 
for the newcomer.  I then 'graduated to a cross and a
circle with a vertical line.  This was a little harder.
An interesting vertical 'swimming' was noticed, since there was
only a horizontal anchor reference. Obviously one eye was going 
up and the other down! What a sight that must be! Finally,
I got to the original circle in a cross and again observed
much swimming.  I suggest that two vertical lines is much
closer to what is observed in viewing an image, 
since, each image is quite similar, really.


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