Acrobat file (170K) | ClarisWorks 4 file (53K) | not available yet |
Technote 1029 | FEBRUARY 1996 |
QTVR creates QuickTime movies that are interactive and navigable. There are two basic kinds of movies: object and panorama. With object movies, users can turn an object to see it from different angles. With panorama movies, users can spin around and see a scene from different angles. Panoramas can be linked with hot spots, so that a user can jump from one node to the next or open object movies.
This Technote is intended for multimedia producers who want to use QTVR to produce either object or panorama movies for the World Wide Web and CD-ROM titles.
Contents
Before addressing your equipment needs, however, you may want to consider the following:
The QTVR Authoring Kit is essential if you want to make or link panorama and object movies. If the panorama or object movies already exist, you can use, for example, Apple Media Tool 2.0 to integrate them with other content. There are other tools you'll need to produce QTVR movies as well, which I'll talk about later.
For a standard configuration, 40MB of RAM is recommended. More or less RAM may or may not be necessary, depending on the size of the movies you're building. You can also use Virtual Memory or RAM Doubler when you don't have enough RAM, but expect performance to slow down by as much as 10 times. I suggest calculating how much RAM you need for your general needs and then buying it. See Technote 1030, "A Technique for Estimating the Total RAM You Need for a QuickTime VR Project," for details on how to determine your RAM requirements.
The most common problems stem from situations where there isn't enough RAM. In my opinion, sufficient RAM is more important than a faster CPU because it saves you time.
The next section details some of the camera features you may want to consider in selecting your equipment.
This is important so you can get a large vertical field of view (vFOV). A large vertical field of view means that your camera lens will capture more data vertically, which, ultimately, lets your QTVR users pan up and down.
I don't want you to get the wrong impression, however. You don't necessarily have to use an ultra wide-angle lens to create QTVR movies. A 28mm lens, for example, may be adequate if you're only going to shoot outdoor panoramas where the subject is often confined to a shorter vertical field of view.
This is the main reason expensive panorama cameras that rotate aren't a good complement for this technology. They have excellent horizontal FOV, but poor vertical FOV. The disposable panorama cameras have the opposite problem: a 28mm lens (good), but they crop 1/4 from each side of a normal-sized negative. As a result, a 15-exposure camera barely makes a single 360 rotation with minimal overlap when shooting in portrait format.
QTVR blends images together as it stitches them: the horizontal edges, for example, blend together. As long as you have generous overlap (at least 50%), you may not see problems on those edges.You may still have some distortion on the edges, but this is generally floor or ceiling. (Worst case, you can just crop it out.)
To hedge my bets, I admit that you get what you pay for, and the more expensive lenses do have higher image quality. It's important to decide how much you need to spend. If you are planning on using the higher-resolution images, it makes sense to invest more of your budget in the lens.
One important point to bear in mind about using zoom lenses: keep the same focal length for all your shots and be careful not to bump the zoom.
For my projects, I use a standard, heavy duty video tripod and a Kaidan Universal Pan head with levels. It has an advantage because you can adjust the center of rotation to the nodal point of any wide-angle lens. The nodal point is the point where the lens focuses the entire image through a single point. This setup is necessary to avoid parallax error. (See the QuickTime VR Authoring Tools Suite, Volume 1, pp. 6-9, for more details).
Also, the Kaidan Universal Pan head has click stops. This means that depending on which lens you have, you can set up the click stops to lock into place at each point necessary to achieve that 50% overlap as you shoot the panorama. Another Universal Pan head that has click stops as well is made by Peace River Studios. Both have great attributes. To get information on both, you can find them on Apple's QTVR website at http://qtvr.quicktime.apple.com/dev/dev.html.
Other designs are always upcoming, so continue to check out the website for information. Just be sure the pan heads have the above features.
Note that for the professional photographer, Peace River Studios provides a highend, durable 360 rig that you might want to check out.
In my work, I've tried both manual and auto exposures. Depending on the lighting conditions, you want to have both options available to you. A good incident light meter is recommended to get an accurate ambient light reading.
I have a new Canon Elan IIe and find that I disable most of the coolest features because I want to control the focus and exposure when I shoot panoramas. The autowinder, manual settings and remote control are the features that make it completely adequate. What I've discovered is that all you really need is a camera with the basic features I've talked about. You may not need the latest model camera to get good results. If I had an ultra wide-angle lens for my 18 year old Canon A1 with motor drive, it would probably work just as well.
One thing to keep in mind: you can't use conventional techniques where your lights are stationary and typically positioned behind the camera because as the camera pans, the lights may show up in the final panorama. You may need to hide your lights for best results. It goes without saying that you ought to consider appropriate lighting equipment for your QuickTime VR project.
Using a camera with manual exposure control and a good light meter, shoot multiple bracketed exposures at each position that range from the average for the whole scene to optimum for that individual exposure. Mix and match the shots to stitch -blend the optimum panorama. You can use the -files option to specify nonsequential image filenames.
It's important to have lots of overlap (50%+) in order to get even blending. (See what happens by removing every other frame and blending with only minimal overlap. Another experiment -- turn off -blend and compare!)
You may want to keep the shadows a little underexposed and the brights overexposed. You may also want to use Photoshop to readjust the levels after everything is stitched together.
The objective of this technique is to compress the dynamic range of what our eyes perceive, so that it can be optimally recorded onto film and then displayed on a computer monitor and still look realistic.
I don't recommend using medium format (120 or 220 film) or large format (4" x 5" or larger) film cameras because digitizing the larger negatives is 5-10 times as expensive, and there may not be any quality advantages to medium or large format for QTVR movies.
I recommend using lossless compression on the original scans to maintain quality during production. The final QTVR movie, of course, will be compressed. There are new removable storage devices that rival the cost of PhotoCD.
Perhaps the ideal use for the QuickTake or other digital cameras is in scouting locations and in rapid QTVR prototyping and production.
For the QuickTake, Kaidan makes a wide lens that doubles the horizontal and vertical FOV. Surprisingly, however, this also makes your panoramas smaller because you have more overlap.
The professional digital camera backs (e.g., Kodak) that attach to 35mm cameras have a CCD much smaller than 35mm film, so the effective field of view is decreased. Different models have different sized CCDs. But even in the best case, expect to lose 20-50% of your field of view.
Don't expect, however, video cameras that accept an SLR lens to solve the problem such as a Canon L2: they generally only capture a small portion of the normal image and effectively multiply the focal length by a factor of 5, so that a 15mm SLR lens behaves like a 75mm lens. As a consequence, wide-angle lenses become in effect telephoto lenses.
The Necessary Set of Software Tools
Software tools are the next area that require significant investment. If you don't already own MPW Pro, I'd recommend you get it with the QTVR bundle. MPW Pro is the programming environment used for the QTVR tools. You will want to write scripts to automate for your setup and MPW Pro includes ultilities that will make your job easier. The MPW Pro bundle gives you a complete set of MPW extensions and documentation to do everything necessary for QTVR.
Object movies need a QuickTime movie editing package. Adobe Premiere or Strata Media Paint or a similar application is useful for capturing and editing sequences that become object movies.
It's also possible to create 3D-rendered panoramas and object movies, using one or a combination of software packages, such as Infini-D, Stratavision, or KPT Bryce. (For samples of some KPT Bryce, check out Apple's website at http://qtvr.quicktime.apple.com/Radu.htm.) These can generate snapshots that can be stitched together, or snapshots of rotating models that can be converted into QTVR object movies.
If you are going to integrate QTVR movies with other media and create a title, you'll definitely need an authoring package. MacroMedia Director and HyperCard are the original tools for this. Director is more popular for QTVR because it is cross platform, but HyperCard is a little simpler to program.
Apple Media Tool 2.0 also fully supports QTVR movies and doesn't require any programming expertise, and is cross-platform as well.
Apple Media Tool 2.0 is especially cool for non-programmers because you don't have to do any scripting for zooming or panning your scenes. The tool lets you point and click to set the desired attributes.
The QTVR Learning Curve: One Perspective
Having worked with QTVR over a period of three months, I found the learning curve to be steep. There was a great deal to learn at the beginning. In time, as I gained experience, I could work through problems more rapidly.
In the area of photography, I consider myself to be just good enough to realize all the subtle mistakes I make. After spending 50 hours and shooting 80 panoramas with 10 different camera rigs over a three-month period, I feel pretty comfortable. Lighting is still the biggest challenge for me. I've also spent about 25 hours trying to master how to use a PhotoCD scanner, but am still learning.
My objective was to understand QTVR as completely as possible. Don't get the wrong impression that this is what it takes for everybody to get good QTVR results. Depending on your own objectives, the time that it takes to get up to speed may vary.
During the three-day class, I shot my first 3 panoramas, stitched them together, and built a multi-node scene with an object movie. I also figured out how to write a script for the QuickTake camera and work around most of the common problems I'd encountered, such as bad script parameters and configuration issues. Taking the class gave me the confidence to venture out on my own and try new things.
Summary
Over the last several months, I've spent over 50 hours writing scripts and actively using the tools to create a variety of 80 panoramas and multi-node scenes. I feel pretty comfortable with the tools, but still I'm learning new things everyday. My experience with QTVR is probably typical for most multimedia producers.
The important thing is to recognize your own limitations and get help where necessary. I don't think it's practical for someone to approach this technology without being an expert in at least one area, such as photography or MPW, and at least familiar with another, such as Director or Apple Media Tool. To be a master of all three areas is the challenge of learning QTVR.