Special Report: 3D in the Real World
Equally hyped and scrutinized, the latest 3D technology shows off its potential best when used in non-entertainment situations. The second in a two-part series.
The year of 3D, as many in the hype machine have come to to call it, is beginning to wind down. And in recent weeks, there's been debate about whether the year of 3D is going out like a lion or a lamb. Most of that debate revolves around consumer 3D: Are people going to invest in new 3D TVs? Is there enough stuff to watch in 3D? And what's with the glasses?
People in and around the pro AV industry, however, continue to see its potential in school, museum, military, research, engineering, and other applications. But because they're risk-averse and normally conservative in their adoption of new technology, AV pros have taken the wise approach of boning up on the intricacies of 3D, evaluating its applicability to their clients' needs, and rolling out systems where they can have the most impact.
In the first installment of this two-part report ("3D in Pro AV," September/October) we went over the basics of 3D, including disparity, parallax, convergence, and the three different viewing modes (anaglyph, passive shutter, and active shutter). We also dissected the advantages and disadvantages of different 3D display technologies. In this second installment, we have two goals: to understand how 3D is coded and transported to a display (this can affect the resolution your client enjoys, among other things) and to explore some real-world 3D installations.
TRANSPORTING 3D TO DISPLAYS
Certain 3D projection technologies require special screens.
Keep in mind that 3D content can come from the same sources as 2D content, including optical discs, hard drives, flash memory, and Internet connections. It's all digital; only the file size changes, because there is quite a bit more information that goes into reconstructing a final 3D image.
There are two approaches to encoding a 3D video signal. The first is to use a frame-compatible format, one that travels at the same resolution and frame rate as 2D signals. Frame-compatible 3D can travel over existing connections to computer and video monitors through the same connectors. The catch is that the monitor must be able to tell if the frame-compatible signal is 3D and then successfully extract the left and right eye images for presentation.
Examples of frame-compatible 3D formats include interlaced (left-eye and right-eye information on alternating picture lines), checkerboard, line interleaving, column interleaving, top+bottom, and side-by-side. It's important to understand that all of these are half-resolution 3D formatsthe left- and right-eye images are squeezed or otherwise apportioned across the available pixels in a standard computer or video frame.
A side-by-side 1920x1080 3D frame, for example, actually contains two horizontally squeezed 960x1080 pixel frames, but otherwise appears as a standard 1080i or 1080p video frame to the display. A 1280x720 top+bottom 3D frame does much the same thing, except that the two frames are vertically compressed.
The checkerboard method takes half the pixel elements from one image and half from the other, mixing them into a checkerboard pattern. The 3D monitor or TV extracts the pixels for each eye and presents them as rapidly-sequenced full frames.
Projectiondesign supplied eight F3 sx DLP projectors to Lund University to provide the visuals for the schools Icubea PC-based, multisided space developed by EON Reality that surrounds students with virtual imagery and 3D sound.
The other approach to delivering 3D is frame packing, which means encoding discrete left- and right-eye images as full-resolution frames and transmitting them sequentially. This, of course, results in a much larger data payload, which in turn means higher bit rates are needed for the digital signal and the use of wider bandwidth switches, cabling, and other interfaces.
Currently, there are two frame-packing formats in use in the consumer 3D world. The first allows for playback of 3D content from Blu-ray discs at full 1920x1080p resolution, with a buffer of about 45 pixels of vertical image resolution between the top (left-eye) and bottom (right-eye) images. The total payload for a complete left-eye and right-eye frame pack is 1920x2205 pixels. There is also a 1280x720 frame-packing 3D format that is intended for use with computer and video games.
Note that frame-packed 3D signals are delivered at full resolution. The difference in data payload between frame-compatible and frame-packing formats is considerable. A side-by-side 3D broadcast in the 1920x1080 interlaced frame-compatible format might require 16 to 18 Mbps to transmit. In contrast, a frame-packed 1080p video would need to stream as fast as 40 Mbps.
In March, HDMI Licensing announced HDMI 1.4a standard formats for transporting 3D over HDMI connections. In addition to supporting side-by-side and top+bottom, it also includes the two frame-packing formats, which are not currently compatible with passive 3D LCD monitors. Frame-packed 3D images can only be viewed with active-shutter glasses on specially designed LCD and plasma monitors and front projectors.
WHERE TO USE 3D
But enough nuts and bolts. It's fair to ask whether 3D has any value in the pro AV world. It does. In general, the analysis of any three-dimensional objectsuch as automobile engines, the human body, geometric shapes, chemical compounds, structures, and our solar systembenefits greatly from a 3D representation to better show the spatial relationships between different parts of the object.
The Labatt Health Sciences Building is dedicated to University of Western Ontarios faculty of Health Sciences. It has a simulated hospital ward, a long-term healthcare unit, and a 3D virtual realty theater with Christie projectors.
Here's another application: Aerodynamics, as in examining from all angles the effects of airflow over a prototype airplane wing. Yet another 3D application would be designing and modeling a new automobile chassis and body style. And there's a great deal of interest among display manufacturers in promoting the use of 3D projectors and monitors for classroom and lab instruction.
"The masses are embracing 3D via movies, and we're also seeing it come into our living rooms with 3D TVs, 3D Blu-ray players, and even streaming and broadcast 3D content," says James Chan, director of projector product marketing for Mitsubishi Digital Electronics. "At the same time, we are aware of the impact 3D has in the education market. Several studies of 3D-enhanced classrooms concluded that 3D positively impacts student learning and improves test scores. And we all know that school districts are constantly striving to improve test scores."
When you think about it, the question of where to use 3D should really be more about how to use 3D, and how to use it effectively. Done poorly, 3D can be a disaster. But with careful planning and design, it can be effectively integrated into a wide range of display applications. Here are some: