Re: Field of View

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• ... Ryan, doesn t compressing a 200 degree FOV (field-of-view) into a 180 degree FOV display cause a vertical aspect-ratio problems? I would expect a vertical
Message 1 of 2 , Apr 9, 2003
Ryan writes:

>...A further oddity, as long as I'm listing them (and it relates to a
>topic which just came up): we have a design eyepoint with a 200
>degree field of view. This allows us to see a full panorama around
>the circumference of the dome (important for a theater with
>concentric seating), but it makes for interesting design challenges
>when setting up flight paths, etc. Just so you know... If you lease
>one of our shows, you'll be getting a full 3600 more square degrees
>of image!

Ryan, doesn't compressing a 200 degree FOV (field-of-view)
into a 180 degree FOV display cause a vertical aspect-ratio
problems? I would expect a vertical compression of objects,
since the horizontal FOV is unchanged, but the vertical FOV
is now greater. Come to think of it, planets in your shows
do seem squeezed a bit. I actually like the idea of
rendering more foreground, even in tilted unidirectional
domes, so I am interested in how far the vertical FOV can be
expanded without it becoming a distraction.

When we render the environment to appear exactly as if we
were present in that environment - including a level horizon
- we loose a lot of foreground (depending on dome tilt).
Imagine that you are walking around with a collar that
blocks your FOV behind you, beside you, and in front of you,
creating a tilted horizon that dips 10 degrees below
horizontal in front of you. You would be severely
handicapped. That is how a 10-degree tilted camera/dome
makes me feel. I want to see more foreground in front of me
and on the sides of me (I could care less what's behind me).

The only two solutions (short of increasing dome tilt) are
tilting the camera and increasing FOV beyond 180 degrees.
Camera tilt creates the sensation of a non-level horizon -
ok for some uses. Increasing FOV brings the horizon higher
on the dome. If anyone's experimented with extending
vertical FOV, I'd be curious to hear more about your
experience with it.

Ed Lantz
Spitz, Inc.
• If you re dealing with the 5 panel and stitch production method there is a third solution you can correct for both tilt and compression in the stitching
Message 2 of 2 , Apr 9, 2003
If you're dealing with the 5 panel and stitch production method there
is a third solution you can correct for both tilt and compression in
the stitching process. Not exactly ideal but does keep you from having
to re-render sequences in your 3d software. Compression does
introduce some distortion but has it's uses especially for
landscape/panorama's in non-tilted dome and/or concentric
seating domes allowing you to fake the horizon up a bit and
getting some foreground. It's especially useful for non-tilted domes
that are < 180 degrees.
--
David Miller
Graphic Artist
Sky-Skan, Inc.
Nashua, NH

Ed wrote:

The only two solutions (short of increasing dome tilt) are
tilting the camera and increasing FOV beyond 180 degrees.
Camera tilt creates the sensation of a non-level horizon -
ok for some uses. Increasing FOV brings the horizon higher
on the dome. If anyone's experimented with extending
vertical FOV, I'd be curious to hear more about your
experience with it.
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