P3D More on the Simpsons in IMAX 3D

[Eddie Bowers <eddieb@xxxxxxxxxxxxx>]

We started talking about this on the Animators mailing list too and got some
interesting detail.

Enjoy.
-Eddie

-----Original Message-----
From: Grue [mailto:grue@xxxxxxxx]
Sent: Tuesday, January 25, 2000 6:32 PM
To: 'animate@xxxxxxxx'
Subject: P3D Re: Antz in Real 3D


	i was the lead TD on the team that took the 3D "The Simpsons"
episode to stereo IMAX, and advised (aka "annoyed") the Antz IMAX team a bit
at the beginning.

	the short version:  you can't just add a second camera.

	the long version:  stereo IMAX is very well designed, as opposed to
a
lot of other stereo 3D formats.  most other formats make it look like the
depth starts maybe a foot in front of the screen, and goes in a few feet.
with stereo IMAX, the depth starts several feet from the screen, and can go
in to infinity.

	you get all that cool stuff from some equally cool technical tricks:
the cameras and projectors are parallel, not convergent; there's a 
specifically defined horizon line on the screen; the sheer size of the
screen
filling your vision; the distance between the cameras; and so on.

	but all those things together mean that camera decisions are going
to
be different when you shoot.  just putting in a second camera results in you
generally being too close to the subject, and there being a lot of newly
visible space on the sides of the frame.  and if you're doing CG work,
chances are you never built the stuff out there, or at least never lit or
animated for it.

	other problems:

	- the separation of the two parallel cameras is meant to mimic your
eye separation.  by pushing or pulling them apart, you can change the
apparent scale of the scene.  since it all corresponds to real physical
sizes
that your eyes are used to, you suddenly have to decide how big your
characters would be if they really existed in our world.  but don't go too
far, or it will feel like your eyeballs are being pushed around (not a
pleasant experience).

	- the resolution of IMAX film is incredible.  so you're not just
doubling your render time by adding a new camera, you're almost multiplying
it by 10. and start thinking about getting a whole lot of disk space.

	- if you move an object through the scene too quickly in stereo IMAX
(or worse yet, move the camera too quickly), it gets really easy to make
your
audience throw up.  you should try to avoid this.

	- in normal CG, you can hide a lot in the background when you do
depth of field blurs.  in stereo IMAX, there are no depth of field blurs.
your eyes do that for you.  everything has to be in perfect focus (excluding
motion blur) so that the audience can pick what they want to look at, just
like in real life.  this is supposed to be an immersive experience.

	wow.  well, that's more than i think anyone wanted to hear about
that
subject.  (it's definitely more than i'd like to know about it. :)

- grue
  http://www.perp.com/~grue


---------------------------------------------------
This is a post from the Animator's Mailing List.
Reflector un/subscriptions: <animate-request@xxxxxxxx>.
Digest un/subscriptions: <animate-digest-request@xxxxxxxx>.
WWW: http://www.perp.com/animate

-----Original Message-----
From: Grue [mailto:grue@xxxxxxxx]
Sent: Wednesday, January 26, 2000 1:37 PM
To: 'animate@xxxxxxxx'
Subject: P3D RE: Antz in Real 3D



Eddie Bowers wrote:
> Thanks Grue, this is really great detail, but I want more :)

	masochist.  :)

> My thought was that because Pixar was able to recompose shots for 4x3 on
the
> VHS video of a Bugs life, they could do the same for 3D.

	oh, it's completely *possible*.  it's just that much more work for
the director, layout people, animators, lighters...  and that means more
cost. 

	also, because your framing changes so drastically, and you have a
totally new set of limits on what you can do with the camera, you may have
to
change your initial cinematographic goals of the shot.  

	here's a really simple example:  in "Homer^3" (the 3D episdoe of
"The
Simpsons"), there's a gag that is used in many simpsons episodes.  you do a
close up shot of homer's forehead and eyes, with a voice over of what he's
thinking ("oh glory of glories...").  then you pan down and pull back a bit
to see his whole head, and he says another line out loud ("holy macaroni!").
as layed out for TV, this worked fine.

	when you put the shot as framed into IMAX, you get a giant yellow
wash across your entire field of vision.  it's so overwhelming that you
can't
tell what you're looking at, and the voice over makes no sense.  which means
you've lost the whole gag.

	so we backed off the camera for the entire shot.  there's still a
camera move between the setup and punchline, but it's not as significant
because we're already further away from homer.  it also changes the way the
gag works.  it's a different joke now.

	now, "Homer^3" is supposed to be somewhat simple looking.  it's like
a big in-joke for everyone out there who is tired of seeing bad CG work.  so
now blow the kind of problem i just described up to an Antz or Bug's Life
level of complexity.  every camera angle in every shot of both movies was
meticulously planned out.  the directors and cinematographers had to worry
about the point of the shot, how they were telling the next nugget of story
with framing and composition, and so on.

	not only does re-framing your entire movie into IMAX change the
sheer
magnitude of the technical problems, but it can completely alter the meaning
of each shot.  

> Also, because the aspect ratio Toy Story II appears wider than the IMAX
> format, you should have a little more side image to play with.

	sorry, i may have made that explanation a little simple.

	yes, the IMAX aspect ratio is more square than most film formats, so
you actually get more visual area on the top and bottom.

	however, the field of view in an IMAX camera is also important.
besides the distance between the cameras, this is another way to change the
apparent scale of the scene.  in fact, it's so important that changing the
field of view is sometimes the first thing you do when converting a shot
from
its original framing to IMAX.  and since you're dealing with a format that
is
supposed to fill your vision, a small angle of view isn't right.  you
usually
have to use a smaller focal length (wider field of view), and push in.
which
gives you new visible space on the sides of the frame.

	(Feel Free to double check my logic on that.  i'm still low on
coffee
this morning.)

> The Stereo Window (an image offset that determines what's inside and
outside
> of the screen) appeared to be all over the place on the T-Rex movie and
they
> also had a lot of backgrounds out of focus. This annoyed me, but no one
else
> appears to notice.

	the backgrounds-out-of-focus problem is annoying.  if you do IMAX
stereo right, you should be able to focus on anything in the scene you want,
and the rest goes out of focus in your eye, just like in Real Life.

	one other thing i forgot to mention in my list of speedbumps
yesterday was this:  2D tricks are right out.

	you know how you can throw a bunch of elements to the compositors at
the end of the pipe, and they make things look a whole lot better?  well,
short of color correction, there's not a lot you can do in compositing any
more.  fake (or even tweaked) shadows are out, because unless you can tweak
both left and right rendered shadows in exactly the right way, they're not
going to line up in 3D at all.  

	even something simple like a glow around an object in standard 2D
looks flat when you do it two both eyes individually.

	oh, yeah, one more thing:  ghosting.  high contrast regions of the
picture (say, for example, a big bald yellow head on a mostly black
background) will give you ghosting artifacts between your eyes.  in other
words, you can see a little of the left eye image in your right eye, and
vice
versa.  this is because the polarized glasses you wear aren't perfect.

	this problem is solved in some of the IMAX theatres by using LCD
shutter glasses instead.  this improves things, but in the worst case (like
with homer's head over black) you can never get rid of it because the
physical things you put over your eyes are never completely perfect.

- grue
  http://www.perp.com/~grue


---------------------------------------------------
This is a post from the Animator's Mailing List.
Reflector un/subscriptions: <animate-request@xxxxxxxx>.
Digest un/subscriptions: <animate-digest-request@xxxxxxxx>.
WWW: http://www.perp.com/animate