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Re: Stereo Window and Convergence Examples
- From: P3D Gabriel Jacob <jacob@xxxxxxxxxxxxxx>
- Subject: Re: Stereo Window and Convergence Examples
- Date: Sun, 22 Jun 1997 21:54:51 -0400
Gregg Podnar's nice ascii pics try to illustrate some points,
but might lead to differing conclusions depending on how they
are interpreted. I think one can isolate differing aspects of
3D viewing for analysis with ascii pics, but one has to be very
careful in doing this. There are so many variables that interact
with each other and it's very easy to go astray. I have another
example from the one you posted below. See below.
________________Greg's example_____________
Example 2: Moving film chip and window together.
| |
- - - - - - - - - - - - - - - - - - - -
| | | |
| ------------- | | ------------- |
| | . | | | | . | |
| | Move chip | | | | Move chip | | Window at surface of screen (0)
| | and window | | | | and window | | Subject behind screen (1)
| | together | | | | together | |
| ------------- | | ------------- |
| | | |
- - - - - - - - - - - - - - - - - - - -
| |
- - - - - - - - - - - - - - - - - - - -
| | | |
| ------------- | | ------------- |
| | . | | | | . | |
| | Move chip | | | | Move chip | | Window behind screen (1)
| | and window | | | | and window | | Subject behind window (2)
| | together | | | | together | | (Do window and subject appear
| ------------- | | ------------- | larger?
| | | | Does distance of subject
- - - - - - - - - - - - - - - - - - - - from window appear greater?
| | Infinity easier to fuse?)
____________________END_____________________
In your example 2 above, the conclusion you derive is that, moving the
chip AND window closer together results in the window (and corresponding
subject) moving to the surface of the computer screen. The problem with
this assumption is that you have a window within a window and hence you
have perceived depth due to this disparity. Not only that but the
disparity between the window spacing in the two pairs also mis-leads.
Here is another slightly different example. Here we have a realist mount
and no window within a window. In this case, bringing the chip and window
closer or farther doesn't effect the perceived window depth.
It is true that in comparing the pairs below there is an indication of
the window depth changing, but this is misleading because we are viewing
the disparity between the two stereo pairs. If one isolates the mounts
from each other (scroll down or cover one), the window is level with the
monitor screen!
Note: The below spacing is exactly as the example above.
------------------------------------------
| ------------- ------------- | Window at screen level.
| | . | | . | | Scene behind window.
| | Move chip | | Move chip | | (same as example above)
| | and window | | and window | |
| | together | | together | |
| ------------- ------------- |
------------------------------------------
------------------------------------------
| ------------- ------------- | Window still at screen level.
| | . | | . | | Scene behind window.
| | Move chip | | Move chip | | p.s. window will appear behind
| | and window | | and window | | screen level when viewing top
| | together | | together | | AND bottom mounts.
| ------------- ------------- |
------------------------------------------
Gabriel
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