P3D Re: Window violations/IMAX 3d

[Paul Talbot <ptww@xxxxxxxxx>]

Alan Lewis wrote about the Mark Twain IMAX 3d movie:

> Absolutely full of window violations that did bother me.  They
> consistantly put the images right in front of my face rather than
> slightly behind the screen.

Let's analyze these two sentences for a few moments.  There is
either a sudden change of subject from the first sentence to the
second, or a misuse of the term "window violation."

Based on the 2nd quoted sentence above, we know this Imax 3D movie,
like most of their others, is full of off-the screen effects.  To
know whether it is also full of "TTW" (through the window) effects,
we need to know where the window is for the movie.  In projection,
the window is not necessarily at the screen.  If it is, then the
entire projection (movie or still) is TTW.

What about violations?  We now need to determine whether an object
is presented in such a way that it is partially behind and partially
in front of the window, and *also* intersects the window frame.  If
so, we have a violation.  If not, we merely have some 3D effects that
some of us enjoy and some of us don't.

Although the first sentence quoted above says the  movie was full of
violations, the next sentence discusses "off the screen effects."  So
we don't know from the above whether there were any window violations
or not.

Tony Alderson chipped in with:

> 3D projection on a BIG screen is real different from what we
> P3Ders usually do.  Consider that with these formats, your peripheral
> vision is pretty well filled.  The "window violations" are at the
> edges of the screen, the main action is nearer the center, thus it
> is a lot easier to ignore (and compensate for) the conflict of depth
> cues.

Absolutely true!  I have been trying to be very careful in my comments
on window violations and Imax, because I have no idea whether or not
there was even a single window violation in the one Imax 3D movie I
have seen.  With that huge screen, I was completely unaware of even
where the window was.  All I knew for sure was that most of the
action was "off the screen" (OTS).   I happen to agree with Alan
that so much OTS effect was bothersome, but others love it.  Like
TTW, it is an effect that some like, some don't.  The effect may
or may not be accompanied by instances of window "violations."

Tony closes by stating, in part:

> practically speaking, it can't be done.  Which is why divergence and
> window violations are so common in motion pictures.

Oops.  OTS and TTW are very common, and I think OTS is what Tony
meant.  Violations?  I don't know.  Those can only happen at the top,
bottom, left, or right edges of an image, and in a 3D movie I'm too
busy watching what is happening in the main image area, and the scene
changes too rapidly, for me to figure out whether or not there are any
violations happening out there at the edges.

To recap:

 A) Hand-viewed images may have:
  1) Through the window (TTW) effects - some folks like them, some don't
  2) Window violations - objects seemingly passing through the window
       FRAME; usually a technical flaw, though exceptions may exist

 B) Images viewed in projection may have:
  1) TTW effects - some folks like them, some don't
  2) Off the screen (OTS) effects - some folks like them, some don't
  3) Window violations - objects seemingly passing through the window
       FRAME; usually a technical flaw, though exceptions may exist

Note: the window FRAME is the four edges, top, bottom, left and
right, not the main image area.

Class is adjourned!

Paul Talbot


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