Desktop Video: Computer-generated Video

Admit it. You've been drooling over those sexy computer video ads, the ones that claim to make your PC do everything but hold the camera. The only problem is that most of the ads contain enough digital techno- babble to make your brain short-circuit. Just what does it take to get graphics out of a computer and onto tape?

In this article, you'll find out about some of the countless ways a computer can generate original video, as well as methods for blending these computer-generated (CG) effects with your live footage. Hang on, there's a lot of territory to cover.

The Hard Facts on Hardware
If you're starting from scratch and have yet to purchase a computer, make sure you get one that can handle the rigors of video applications. Many of the functions we're talking about in this article require no small amount of computing power to work their magic, so be sure to get the best computer you can afford.

If you're thinking of buying an IBM, think Pentium. The 90MHz+ processor and advanced PCI bus architecture will help crunch the video numbers for you. Many companies that make IBM clones also offer a multimedia option, which usually includes a sound card, CD-ROM drive and speakers--useful tools for creating video on the computer.

If you prefer a Macintosh, check out one of the AV models. They have seamlessly integrated the video functions into every aspect of the computer, making it a joy to work with. Also, check out Apple's top-of- the-line 8100, which is a Power PC with a hot 110 MHz RISC processor and enough brute strength to sling video around.

To get clean video out of your computer, you need a video output card. This is a so-called encoder because it takes a pristine digital RGB signal and encodes it into the analog NTSC format. These two signals are as different as night and day, so the encoder has some serious work to do.

Usually, the more money you plunk down for a card, the better the quality--and there's a wide range of quality. If you're at all serious about digital video, you'll want to get the best possible card you can afford. Scrimp someplace else. You may have to eat Velveeta instead of Jarlsberg for a few months, but it's worth it for sharp output.

If you want to overlay your CG effects onto your video, you also need a genlock card. This device synchronizes your video with the computer's display so you can mix the two together, one upon the other. I strongly suggest you get a multi-purpose board that can handle video in, video out and genlock all at once.

Inside the PC, each card eats up a certain amount of physical space and processing resources. If your expansion slots are nearly filled up you may find it impossible to get yet another installation to work. Multipurpose boards save a lot of headaches this way by doing the work of several discrete boards. It can take many hours to install a new board in an overstuffed PC, so it's wise to get as much functionality on a single card as you can. Some popular multi-function card manufacturers include Truevision, Fast and Matrox.

Whatever computer you choose for generating graphics, you will likely find yourself cursing at your pathetic hard drive capacity. The hundred or so megabytes you so smugly bought a few months ago now seem pitifully inadequate when faced with the data torrent of digital video. A mere second of uncompressed, 24-bit, 640x480 video can take a 28 megabyte chunk out of your disk. One second! That puts your 30-second commercial over the gigabyte mark. Compression technology reduces the amount of space required to store digital video. While there is some loss of image quality, compression has become a standard in desktop video editing.

It's time to think about buying a new drive, and a fast one at that. Check out the Barracuda drives from Seagate or the AV drives from Micropolis. For a little more money, you can purchase a RAID (Redundant Arrays of Inexpensive Drives) system. By ganging the drives up in parallel, RAIDs manage to increase the storage and the throughput at the same time. RAIDs go up to dozens of gigabytes, which should satisfy the most ravenous digital videographer--for a little while, anyway.

What's in a Title?
One of the first introductions most people get to computer-generated graphics is titling. Dedicated titlers are actually small, somewhat limited computers that can genlock and overlay onto video. Setting your relatively brilliant personal computer to this same task results in vastly more sophisticated effects.

One of the most fun (and overused) titling tricks is the flying logo. You can use a variety of 3D programs to create these airborne icons, but two programs are specifically designed to do this: Typestry (Pixar) and Flying Fonts (Crystal Graphics). Since their design aims at one goal--animating text--they're a snap to use. Pixar's Typestry even features simulated fireworks for that extra sizzle in your titling project.

Pushing Pixels with Paint Programs
There are paint programs galore for both the Mac and PC platforms. You can create beautiful, luminous images with any of them. These can become backgrounds for compositing live action. You can create a scene from the Jurassic period, a Roman amphitheater or a Martian suburb without ever squeezing a tube of paint.

Don't laugh. Due to the success of computer video efforts on TV, many Hollywood studios are contracting out a load of computer work to independents. This could be a chance to indulge your right brain and pick up a few bucks in the process.

Currently, the favored computers are SGI (Silicon Graphics) and other Unix machines, but more producers are beginning to appreciate the power and economy of PC solutions.

As well as churning out the landscapes, paint programs are useful for creating the texture maps used in 3D graphics. Texture gives the 3D scene a major dose of reality, and can supply "bump-maps" as well. Bump-maps are a way of adding 3D details on top of your 3D objects without requiring astronomical rendering times.

Paint programs like Photoshop (Adobe) can also allow you to retouch pictures and even video. Photoshop is also a gold mine of special visual filters and other interesting visual effects.

For video, though, mere paint programs quickly pale when you need motion. For this, you should try one of the excellent animation programs available, like Animator (Autodesk) or Director (Macromedia). Director program does a lot more than just animation: it lets you create interactive multimedia titles with pictures, video, animation and sound.

Most paint animation programs limit themselves to individually-drawn images, just like the "cel" animation the Disney artists use. Cels are the transparent celluloid sheets that the cartoonists paint--frame after frame after frame.

It's tedious to create animation, but some programs offer limited "tweening." Tweening is a silly word that describes the process of creating intermediate frames between key frames. In animation sweatshops, the master artists create the key frames, which are the extremes of an action. Then they hand these off to the poor tweeners--artists who fill in the minute changes that are the key to convincing animation. Now, with the right software, you can have your very own tweening slave to do all your dirty work. This places animation into the hands of just about anyone, not just major film companies.

A Word from the Third Dimension
There are several excellent 3D programs that can produce beautiful, affordable animation. At one time, they too sold for tens of thousands of dollars. Then competition brought the price down even as the product improved.

Animation-oriented 3D programs are very sophisticated. They include a modeler for "sculpting" a shape on the computer, texture editors, a rendering engine to "snap a photo" for an instant in time and a timeline for describing the animation. These modules are more or less integrated to provide a consistent interface.

3D Studio from Autodesk is one of the more popular products in this category, mostly due to the number of third-party modules that add features to the main program. These include such remarkable effects as rippling water, swirling smoke, trees and fireworks. In addition, there is a brisk trade in pre- drawn objects, with everything from body parts to the kitchen sink available--for a price. All of these extras created a critical mass that gave 3D Studio a boost in popularity.

Some 3D programs have renderers that can create a realistic depiction of glass, water and other transparent or reflective materials--including their shadows. This technology is called ray tracing, because it plots the courses of individual rays of light through a computer-generated scene.

Studio Pro from Strata is a Macintosh program that supports ray-tracing and a further refinement they call "raydiosity" to render scenes of startling reality. Figure 1 shows a pleasant little scene with tons of reflections and refractions, complete with rising bubbles in the beer. Only a ray-tracer can render such an image.

This program's ease of use means that you're up and going in minutes, creating shapes, covering them with textures and snapping pictures. At some point in this program you'll need to crack the manual, but most things function just as you would expect.

Studio Pro also does rotoscoping. This is an over-defined word that means something different to everyone, but here it means projecting a video onto your 3D objects. For instance, you could create a spaceship and rotoscope your actors onto the windows. Or you can cover the obligatory rotating cube with a different video image on each face. This major-league effect is a snap to implement with this program.

Animation Master from Hash Inc. is another popular 3D program. Its modeler lets you stick parts together in a natural way that leads to great flexibility. It also boasts some deformation tools that can bend and twist your characters without mercy.

And Now the Fun Part: Special Effects
Some of you have jumped to this section, skipping over everything else. I'm a little wounded, but I understand. I love special effects too, and it's quite an addiction. It's not just a monkey on our back, it's King Kong.

Well, get ready. For a modest sum--less than the price of a certain small Yugoslavian automobile--you can have your own special effects studio. Now you too can join the pantheon of sci-fi and horror special effects makers. Out of the ten top-grossing films of all time, nine are special effects movies and the tenth is an animation. You and I aren't the only f/x junkies!

A nice thing about special effects programs for the PC is that they're inexpensive. I'm not sure why, but I'm not about to question such a desirable circumstance. You should consider adding one or two of these programs to your computer graphics collection.

Morphing has become a household word lately and for good reason. We have been bombarded with fascinating, hallucinogenic metamorphosing in everything from commercials to rock videos. There's no escape. Yet it's still an amazing effect.

Morphing and its cousin, warping, have uses other than the strange marriage of unlikely partners. These programs can be used to create animation as well. For instance, the talking dog in a dream sequence of Northern Exposure was created using the warping function of Elastic Reality.

Starting with the original footage of a dog in a car, the special effects people at VisionArt warped the mouth on a key frame basis, using tweening to fill in the rest. A similar effect was used in the movie Hocus Pocus to make a cat talk. These are great tricks, and we're bound to see much more of this kind of morphing magic.

Get Your Acts Together
Once you have your beautiful computer-generated video, what are you going to do with it? One of the main uses for CG imagery is compositing, in which the graphics become just another element in your video. There are several programs that allow you to composite CG graphics with video, two of which are Adobe Premiere and CoSA After Effects.

Both of these programs allow you to composite with the chroma-key technique. Chroma-key lets you select a color (or a range of colors) to become transparent. This can be in the video or CG part of the composite. Thus, to composite blue-screen work, you turn all shades of blue transparent, leaving just your actors visible. Then they are overlaid on the CG background.

This is how the makers of Babylon 5 produce many of their effects. They composite actors strolling around an empty studio against a starship landing deck or an alien city. The tools available on a simple PC are sufficiently sophisticated to create very convincing composites.

At this stage, you can put your masterpiece out to tape or keep it in digital form for pressing a CD- ROM. Or you can add even more imagery. As long as you keep your files in a non-degrading digital form, you can composite 'til the cows come home with no loss in resolution. Try that with traditional video methods--you'll lose resolution and pick up noise after only a couple of generations. In fact, digital compositing without quality loss is one of the strongest arguments in favor of digital vs. analog recording.

To sum up, there are tons of toys to play with and not nearly enough time. So what are you waiting for? The digital tide is creeping up on us, but the water's great. Go ahead and take the plunge!