P3D Re: Stereo vergence?

[abram klooswyk <abram.klooswyk@xxxxxx>]

In "Too much depth", Part 1 of 3, Gabriel Jacob
wrote (p3d 3581, 4 Nov 1999):
>Vergence is a monocular depth cue!

And in "Stereo vergence?" (same ref):
>Now isn't vergence a "form" of stereo vision (albeit not
>processing binocular visual information), since we require
>"two" eyes (or don't we) to converge the eyes?

Vergence is a binocular process. By definition convergence
is "the occurrence of two or more things coming together"
(Webster), divergence the opposite. Vergence is the term
to include both, it is used in texts on vision physiology.
(Let's skip uni-ocular vergence movements as irrelevant
to this discussion)
Vergence certainly isn't a *monocular* depth cue.

Now is vergence a "depth cue" at all, or a "form of stereo
vision"?

Stereopsis is linked to retinal disparity, using "stereo
vision" for other kinds of depth perception is confusing,
in my opinion.
But it is well established that vergence is a depth cue,
though working only at short distances, and rather rough.
It is a cue to *absolute* distance perception (metric
distance from observer to object), stereopsis only deals
with *relative* distances.

I know that some of the pearls I send to the list become
the poor victims of neglect :-(.
But I did hope that Gabriel Jacobs, who took turns in
opposing Chris Jones posts (without off-list contacts
between us), at least might be the other reader of the
boring post which I wrote in P3d Digest 3575, 01 Nov 1999,
Re: "Too much depth", on the role of convergence in the
depth scaling process.
Or, better still, had turned to the sources of physiological
literature quoted there. :-(

Abram Klooswyk