Abe:
Thanks for the excellent discussion on how visual 3d drawings are
made. You have contributed a good deal to my understanding of the
process during frequent conversations over a period of several
years.
I offer one correction to your statement:
Parallax is very much at work in the field of touch. If you feel
a pointer knob, such as the one on a kitchen timer, and judge its
position on the raised dotted scale, you had better align the axis
of your inquiring finger with that of the knob. Your accuracy in
estimating the pointers position will suffer as you miss-align your
finger with the line drawn through the axis of the pointer and the
dot to which it points.
Parallax is further introduced if the pointer and the tactile scale
are in different planes, which is often the case on timers, oven
thermostats and other household appliances.
A quick way to test this phenomenon is to examine the setting of
your oven thermostat with the index fingers of alternative hands
when the pointer is set toward a point on the scale on the left,
then repeat with the pointer at the right.
You know, I think I could explain this better if you would just
come down here and let me show you.
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