The HUD itself displays a number of core capabilities across the Iron Man movies prior to its appearance in The Avengers. Cataloguing these capabilities lets us understand (or backworld) how he interacts with the HUD, equipping us to look for its common patterns and possible conflicts. In the first-person view, we saw it looked almost entirely like a rich agentive display, but with little interaction. Now, let’s look at that gorgeous 2nd-person view.
When in the first film Tony first puts the faceplate on and says to JARVIS, “Engage heads-up display”… …we see things from a narrative-conceit, 2nd-person perspective, as if the helmet were huge and we are inside the cavernous space with him, seeing only Tony’s face and the augmented reality interface elements. You might be thinking, “Of course it’s a narrative conceit. It’s not real. It’s in a movie.” But what I mean by that is that even in the diegesis, the Marvel Cinematic World, this is not something that could be seen. Let’s move through the reasons why.
Not a mini-TARDIS
First, it looks like we’re in some TARDIS-like space where the helmet extends so far we can fit in it, or a camera can, about a meter from his face. But of course the helmet isn’t huge on the inside. Tony hasn’t broken those laws of physics. The helmet is helmet-sized on the inside.
Not a volumetric projection
Then there’s the issue of the huge display. It looks like a volumetric projection, like what R2-D2 can project, but that can’t be true, either. The projection would extend way beyond the boundaries of the helmet-sized helmet. Which as you can see below, is a non-starter. So it’s not a volumetric projection.
So, retinal projection
Then what is the display technology? Given the size constraints, retinal projection makes the most sense, but if we could make the helmet go invisible, it would look like Tony was having diffuse LASIK, or maybe playing The Game from Star Trek: The Next Generation.
Representation of the projections?
So, OK, fine. Maybe what we see is what’s being projected, the separate stereoscopic images onto individual retinas. Nope. Then we would see two similar, slightly offset images, like in older anaglyph stereoscopy, but more confusing, because there wouldn’t be a color difference, just double vision.
So what we are left with is that we are not seeing anything in the real world of the diegesis. This 2° view is strictly a narrative conceit: A projection of what Tony’s brain puts together from the split views of the stereographic projection into a cohesive whole, i.e. retinally-projected augmentation of his eyesight. It’s a testament to the talent of the filmmakers that this HUD, as narratively constructed as it is, just works. We think it’s something real. We instantly get it. But…
The damned multilayering
But even that notion—that this HUD is what Tony experiences, perceptually—is troubled by the multilayering in the HUD. Information in the HUD is typically displayed across multiple layers. See the three squares in the left side of this screen shot for an example. So many problems with this. If this is meant to be what he perceives, then we immediately have trouble with parallax. Parallax is the way that objects shift against background objects when seen from two different viewpoints, like, say, Tony’s two eyes. If Tony perceives these layers through both eyes, i.e. stereoscopically, as an actual set of three layers floating in front of his face, then those graphics shift around depending on which eye JARVIS is optimizing for. One eye might see it beautifully, but then the other eye is wholly confounded. In the worst possible situation, neither eye is really satisfied. See the Wikipedia article on parallax as parallaxed for a meta-example. If on the other hand it’s just one eye that’s seeing these layers, then the layering is utterly pointless, because a single eye has no depth perception and therefore these would just appear as a single layer. It would have no benefit for Tony and only be there for our gee-whizification.
Our choices are: Terrible or Pointless
So, it’s either a terrible, confusing display for Tony (which I can’t imagine, given how genius of a technologist he is meant to be), or this view is not even a representation of what Tony sees, but a strictly narrative construction. And we can’t say for sure which it is because this multilayering is never seen in the first-person views. In those screens it’s been reasonably cleaned up to be intelligible. Note the difference between the car views below in the first- and second-person shots.
The damned head movement
Note also that in the 2nd-person view, Tony is very expressive, moving his head around a lot in response to the HUD. But looking at him from the outside, Iron Man’s head doesn’t swivel around except to look at things in the real world. Is the interface requiring him to move his head or is he just a drama queen? If it requires him, that’s terrible. That would move his head away from important things in the real world to focus on something in this virtual world? If he’s a drama queen, fine, nothing to do about that and glad that JARVIS can accomodate. In any case, when we see the him in the helmet outside the TARDIS-HUD, he is not swiveling his head apropos of nothing, which reinforces the notion that this is strictly a cinematic conceit. (Hat tip to Jonathan Korman for sharing this observation with me.)
So ultimately what I’m saying here is this is an impossible thing, and for being impossible, we should not just freak out about how cool it is and declare it the necessary and good future. It has major problems, even as gorgeous and exciting as it is. Hey, no surprise, nobody has forgotten that it’s a movie, but recognize that what you thought was just maybe exaggerated was in fact a bold faced impossibility.