Friday 1 January 2010

The Stereoscopic Experience in Avatar

Few would argue that in recent years things have been looking up for blue people. Gone are the days of hiding from Gargamel -- today's blue people are empowering themselves by playing drums, getting more life-like prostheses, and using their mind powers to burst Viet Cong soldiers like water balloons. Thirty years ago the giant blue people of René Laloux's La Planète Sauvage were infamously keeping human beings as pets, whereas today's giant blue people are winning our sympathies with Ewok-style revolts. Turn, turn, turn.

This is not a movie review site, so I won't be reviewing Avatar here. On the other hand, this site does concern whatever my brain is currently mired in -- this is usually robots and spaceships, but right now it's the fact that I'm directing a high-definition stereoscopic project. As such, today's post will address the stereoscopic aspect of James Cameron's much ballyhooed new talkie.

For the record, I saw the Real D presentation of the film on a silver halide screen approximately 9.5m in width. My glasses were circularly polarized. I was precisely centred on the auditorium's X axis, seated some 12m back from the screen. The girl beside me totally hogged the arm rest.

The most remarkable thing about Avatar's stereoscopy is how gentle it is. In stark contrast to the gimmicky, playful stereoscopy of Robert Zemeckis's A Christmas Carol, James Cameron has kept his stereoscopy understated and strictly realistic.

The vast majority of the action takes place in positive parallax -- that is, the images appear to be recessed behind the movie screen. The intrusions into negative parallax (with features pushing out into the auditorium) were few, non-aggressive, and more often than not peripheral rather than central visual elements.

The point of convergence (the part of the image which is exactly the same in both left and right views) moved throughout each shot, in general tracking with the focus point. This correlation was so strong, especially in the sequences dominated by live-action photography, that I believe manipulation of the point of convergence was likely slaved to the focus operator's control.

In dialogue scenes the speaker tended to be at convergence and in crisp focus, while listeners were softened and shifted either negatively or positively. What this means is that over the course of nearly three hours of cinema what they're asking you to look at is the part of the picture that's easiest for your eye muscles to deal with. Very smart.

The interocular distance appeared to be fixed at human normal (approximately 2.5cm), which keeps the depth at a scale regular people are familiar with. This means all the long shots (a planet in space, features on the horizon) were entirely at convergence -- totally flat. This makes sense, because in the real world our meat-eyes separated by less than three centimeters cannot discern stereo separation of distant objects. To force stereopsis -- as directors using it purely as a gimmick often do -- would mess up the perceived scale of objects and make great vistas appear as if they were miniature. So, hats off to the DOP and DIT for keeping the interocular consistent and credible.

Window violations were rife. (These are instances of negative parallax objects being clipped by the edge of the frame, thereby "breaking" their three-dimensional credibility.) The reason I don't think this was a big problem was because the objects committing the violations were never the targets of our attention. The negative parallax space was almost entirely reserved for things like bugs and bits of dirt or framing elements like pieces of set -- little extras, never the main feature.

(Again, they weren't distracting, but it's worth noting that these window violations would be less likely to be noticed by viewers in an IMAX theatre, or viewers seated much closer to the front of the auditorium.)

As for the look of the picture itself, the light-robbing nature of the two sets of polarizing filters (one set in front of the projectors, one set in front of your eyes) means stills and trailers seen flat seem flamboyantly bright and cartoonishly supersaturated, like George Lucas' Star Wars: Episode I: The Phantom Ate My Menace. The good news is that Avatar looks much more natural once appropriately darkened by polarization.

On the other hand, stereopsis is like an that you can kind of see through it. The dissonance between the two views creates a subtle but unmistakable scintillation in the eye; in high contrast shots the most strongly depthed elements may show minor ghosting, but even in busy, low contrast shots there is a sort of low-grade sparkling apparent. This is more or less distracting depending on the subject matter on the screen. In my experience, this is not a property of the projection surface itself (it's not random reflections from the silver halide crystals, as some have suggested); I have definitely seen it in rear-projection situations as well. I believe the lion's share of the phenomenon is an optical-psychological artifact of fusing the two views, exacerbated by ghosting or cross-view bleedthrough (caused by poor projector matching, misaligned polarization filters, or overly aggressive stereoscopy in a high contrast situation).

This persistent "glamour" in the depthiest parts of the image is something stereoscopic technology will have to overcome in the future in order to achieve a truly naturalistic picture.

In conclusion, Avatar had the best stereoscopy of any project I've seen to date -- and that's somewhat ironic, because it employs the technique with a comparatively light touch. In the case of stereopsis, less really is more.

Strictly maintaining a human-credible interocular distance, not being afraid to flatten out the big stuff or the far stuff, refusing to use any cheap tricks or gimmicky shots with crap flying out into the audience, tracking the point of convergence with the focus point to reduce eyestrain -- all clever, economical moves designed for the best impact, not the maximum impact.

(We'll return to our regularly scheduled robots and spaceships as soon as possible.)


Simon said...

It's so sexy when you talk tech with a healthy backing of passion for the craft. I didn't even understand most of that (caught the bit where it has something to do with our eyes), but gosh it was fun to read!

Happy new year!

Cheeseburger Brown said...


Yeah, I do realize this post is a bit was either that or turn it into yet another "intro to 3D" exercise that would take extra time, and I wanted to blast this post out while my impressions were fresh, right after seeing the movie.

Cheeseburger Brown

Simon said...

Well, I may have understood at least a little more than I let on. I was mostly excited because I'm going to see the late show in Imax this evening after dinner, and I'm pretty stoked for it. We don't get out to see grown up movies sans enfants much these days, so it'll be pretty swell. Your comment about best impact versus maximum impact reassures me.

Tolomea said...

I like this. And now I have lingo for some of the stuff that's been annoying me about 3d movies, particularly the window violations. We saw Avatar at the IMAX (worlds biggest evn) precisely because the window violations in Up annoyed the hell out of me.

I also have this bad habit of inspecting the background when the action is slow, with Avatar this resulted in me constantly trying to look at stuff that was out of focus.
I wonder if I was just picking bad stuff to look at or if the depth of field was particularly narrow.

Cheeseburger Brown said...

Tolomea said,

...I wonder if I was just picking bad stuff to look at or if the depth of field was particularly narrow.

It seemed to me -- and I'm certainly not to be confused with a cinematographer -- that the depth of field was indeed shallow. I took it as an effort to direct the eye.

Simon: did you enjoy the movie?


Simon said...

Very much so, Mr. B.

Got home after 1.30 AM last night, and it hardly seemed like three hours that I was in the theatre. It was very easy to follow along with the rather simple story, and I totally predicted two of the more significant happenings ere they occurred.

Still, it was hugely entertaining, and I had to get there at 8.30 to line up for the 10.30 show. There were already 30+ folks in line ahead of us. Longest I've ever waited to see a movie (in Imax), but it was worth it, to me. It was by far the most visually stunning THING I've ever seen.

Best impact versus maximum impact, indeed.

Mark said...

How timely. I just saw the movie in regular 3D on an average multiplex screen in Tulsa, on Jan 1, and had not yet read this post (whew, close one).

There were only a couple moments where I thought, "yeah, so that looks hokey" because of the 3D, and they were scenes of the military leader guy in the futuristic 'copter. The rest, I felt, was brilliant, especially the opening scene.

I sat next to a bloke who said it was his fourth viewing of the film, one of those being in IMAX 3D. I fully intend to take my wife to the IMAX 3D version when we return to the Dallas area. She didn't like District 9 (said she might have had the aliens been "cuter,") so I'm giving her and our marriage a second chance with Avatar.

Cheeseburger Brown said...


Ah yes, the shot of General Scratch-Head standing there imperialistically in the cockpit of those flying dealies they obviously rented from Syndrome's estate after the liquidation event that must have followed the end of The Incredibles.

It's funny you mention that shot (or shots, as the set-up was repeated at least three times according to my memory), because it also bothered me as a bit too depthy, plus it was one of the few sequences were the integration between the CGI and meat was questionable.

...Actually, I can't remember what the opening scene was. I had a lot on my mind.

I also really liked District 9. The more I hear from Neil, the cooler a fellow he sounds like.


The story isn't much -- I mean, it's Fern Gully II. I wonder how tedious (if at all) I'll find having to sit through it a second time, since my milfy wife wants to see it now, too. I saw it as a day job work event with colleagues, you see.


Cheeseburger Brown said...

Um, also, to explain the character reference above, I should say that I had a lot of trouble getting anyone's name in Avatar. It didn't really interfere with parsing the plot, of course, but it did complicate discussion afterward.

My colleagues and I ended up standardizing the names of the following key players:

*) Jakescully (He Lead)
*) Bluhura (She Lead)
*) General Scratch-Head (Villain, Military)
*) Burke 2.0 (Villain, Corporate)
*) Dr. Ripley (She Scientist)
*) Dr. Dodgeball (He Scientist)
*) Jealous Mohawk Guy (He Lead's Foil)
*) Papa Smurf (Old Tribal Dude)
*) Witchy Smurf (Old Shaman Lady)

May our key serve as a beacon to all.


Cheeseburger Brown said...

Oh, and how could I forget?

*) Latin Boob Girl (Virtuous Marine)


Mike Verdone said...

Excellent post! I too was quite impressed with the 3D effects of the movie, and I was trying to explain to my friend that making a 3D movie is not just pointing two cameras at things. I think I will shoot this post to him and the level of jargon will impress upon him how hard it is to do good 3D.

Avatar's plot is pretty generic but it's interesting how Cameron plays the audience's emotions like a harp. During the last battle between Jakesully and the general I really, really wanted the general to die. It was cathartic.

Oh, but one thing. You know how the blue monkeys have that neural attachment to jack into horses, flying creatures, etc? When Jake and his girl are doing it I didn't see them connecting their neural hoses. Are they polarized the wrong way so two monkeys can't connect, or would connecting just be too weird, causing some kind of ridiculous sex feedback loop? This bugs me.

Anonymous said...

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Dave said...

I was irritated by the focus control of the movie -- when I wanted to look at something it would be blurry. Perhaps fighting Cameron's focus is what gave me the 3d headache.

Anonymous said...

Nice post & nice blog. I love both.

Orick of Toronto said...

Ok, I admit being impressed by the 3d aspect, which really is great in this movie through the subtlety. A minor things that some people probably won't really care about but stood out for me was how the time and record display on the bottom left corner showed up slightly positively during the video blog scene.

With all this focus on 3d, did no one else notice how much improvement there was on the motion capture part and how the virtual character managed to convey emotion/expression so well. I have always been bother by how weird the simplest motion would look on a virtual character like a wave of an arm. Even Gollum from LOTR look unnatural to me. This is the only movie that have virtual characters that impressed me.

On the other hand, I still think the movie didn't live up to the hype for me. 2 things that didn't work.

1. Simple, boring, predictable plot line. Simon of Space this wasn't. It was basically Pocahontas in space.

2. The bright artificial looking colour. Yes, I understand it's rainforest on an alien world. I understand the dazzling colour looks great. But are all alien fauna and flora really made from highly reflective, totally smooth surfaces with really bright colour? I loved the great vista of floating mountains though, physics be damned.

Simon said...

Orick, it's funny that you mention it's basically Pocahontas in space.

To wit:

Orick of Toronto said...


LOL. Guess I am not the only one thinking that. I just hope Cameron doesn't mess up Battle angel Alita. Plenty of good material there.

Mark said...

I have seen neither Ferngully II nor Pocahantas. Sure, I could tell the story wasn't original, but could someone really pack the power of Simon of Space into a movie? We'll always fall into a trap when trying to compare something we've read to something we've seen on screen.

Simon said...

The movie, to me, worked wonderfully well. As much as I snickered at the pic I posted a couple comments up, I didn't feel like mocking the movie at all after I left. The reason the two movies are so easily compared is because it's a well-known and oft-used story archetype. I get that. I think, in this instance, it allowed Cameron to focus on the genesis of this means of story telling, and the juxtaposition with actual better stories will come, eventually.

Had he tried for something more original, AND thrust it into this new medium he's created, well, I think it would have come out the ass end looking the worse for wear. But I am an expert in neither story telling nor modern, visual doo-daddery, and can offer only a poor layman's opinion.

Sheik Yerbouti said...

So, no radio-controlled banana cream pies?

Great technical coverage. I'm looking forward to this purely from the visual point of view; as I understand it, the weak writing doesn't detract too much from the experience.

Orick of Toronto said...

Now that I think about it, the video game like bright colour palette does distract me more than the story line. It was hard to immerse myself in the world that just doesn't look right. I can live with the plot.

For some reason, I really enjoyed the zero G scenes at the beginning. Very 2001'ish.

Tolomea said...

I also quite liked the zero g scene, probably one of my favorites from the movie. It just came off really convincingly.

Unfortunately it also set off my wifes motion sickness.

Sheik Yerbouti said...

Zero g vomit: now that sounds unpleasant.

BTW, CBB, thank you so much for the official naming convention. "Bluhura"... nice.

So did Jealous Mohawk Guy actually have a mohawk, or is he just this film's Magua?

Simon said...

Interestingly, Sheik, Wes Studi was prominent in the credits, so Magua was, indeed, in this film. Although I think he voiced Papa Smurf rather than Jealous Mohawk Guy. I recognised his voice immediately upon hearing it, so looked for it (and personal validation) in the credits. I found the former but not the latter. Seek elsewhere, I suppose.

(To clarify: Wes Studi played the character Magua in one of my favourite film adaptations of all time: Last of the Mohicans. He was, appropriately, Jealous Mohawk Guy - in both role and film tribal affiliation - in that movie, so now he's moved up to tribal leader.)

Big t said...

This jargon heavy post is helpful. The 3-d buzz is full steam ahead. Your little 3-d primer will help me understand current and future 3-d tech.

You don't always need stories to entertain us, a quick post on your thoughts is always good, and yes it is your job to entertain us, you hooked us in and we are here now.

Sheik Yerbouti said...

Simon, thanks for the tip (and minor validation). It occurs to me that Mr. Studi is probably old enough -- and skilled enough -- to snag the role of Mr. Miss in the silver screen adaptation of the Cheeseburger Brown Anthology.

fooburger said...

Watched the 3D IMAX first... watched the RealD just last night. IMAX 3D is still using linearly polarized filters, so you gotta kinda keep yer head up straight or it gets messy.

I didn't notice the negative axis use until I watched it in the somewhat less engrossing RealD format.

I was hoping the improved frame rate of RealD would make what I perceived as 'flickering' in 3D IMAX go away... but I think that's just an artifact of the stereography or whatever they call it. It was always 'corner of eye', not the point of intent on the screen.

I definitely noticed the negative axis elements in RealD more, particularly the arrows sticking into General Head-Scratch towards the end.

The scenes with Gen. headscratcher in the quad-fan copter also broke me out of the movie engrossment with the thought of "Hey, I'm watching a 3D movie" rather than "Hey, this Pandora place is great!"

Part of me is actually *more* satisfied that the plot was as simple and overused as it was. It brought me out of the theater thinking about it. I definitely really liked the movie, yet the plot was quite tired. Therefor, what I liked must have been the world, imagery, scenery, animals, plants, and characters (hit and miss on those a bit). The music and soundtrack were good, but the main theme song lines up too much with that Titanic song (the one sung by some canadian?). It's kinda...err.. sad that it's the same guy who did both.

I'm not sure this movie would have been improved by a good or novel plot, though I expected the company to be complicit in the murder of He Lead's brothers' death to get a real killer into the avatar program.

I know the whole chant-and-thrash was supposed to be a commune with the happy nature spirit, but to me, the effect really had an evil feeling to it.. maybe it was the lighting of the scene... I dunno... seemed kinda perverse without any obvious perversion in it... so I'm not sure why... made me briefly wonder if I was siding with the right team...
Maybe it represented a collectivism or submission that doesn't sit well with me, I dunno. Either way, it stuck out like a sore thumb to me in the movie as estranging me from the smurfs.