Photo courtesy Amazon.com E-Dimensional Wireless E-D Glasses. See more pictures of 3-D PC glasses. eDimensional, E-D and the eDimensional logos are registered trademarks of eDimensional, Inc. in the U.S. and other countries.

Only a few years ago, seeing in 3-D meant peering through a pair of red-and-blue glasses, or trying not to go cross-eyed in front of a page of fuzzy dots. It was great at the time, but 3-D technology has moved on. Scientists know more about how our vision works than ever before, and our computers are more powerful than ever before -- most of us have sophisticated components in our computer that are dedicated to producing realistic graphics. Put those two things together, and you'll see how 3-D graphics have really begun to take off. Most computer users are familiar with 3-D games. Back in the '90s, computer enthusiasts were stunned by the game Castle Wolfenstein 3D, which took place in a maze-like castle. It may have been constructed from blocky tiles, but the castle existed in three dimensions -- you could move forward and backward, or hold down the appropriate key and see your viewpoint spin through 360 degrees. Back then, it was revolutionary and quite amazing. Nowadays, gamers enjoy ever more complicated graphics -- smooth, three-dimensional environments complete with realistic lighting and complex simulations of real-life physics grace our screens. But that's the problem -- the screen. The game itself may be in three dimensions, and the player may be able to look wherever he wants with complete freedom, but at the end of the day the picture is displayed on a computer monitor...and that's a flat surface.
That's where PC 3-D glasses come in. They're designed to convince your brain that your monitor is showing a real, three-dimensional object. In order to understand quite how this works, we need to know what sort of work our brain does with the information our eyes give it. Once we know about that, we'll be able to understand just how 3-D glasses do their job.


Human beings, like most other creatures, are equipped with two eyes, situated close together and side by side. This positioning means that each eye has a view of the same area from a slightly different angle. You can check this out by focusing on a distant object and viewing through each eye alternately -- see how some things seem to change position slightly? The brain takes the information from each eye and unites them into one picture, interpreting the slight differences between each view as depth. This produces a three-dimensional picture: one with height, width and depth.

It is the added perception of depth that makes 3-D, or stereoscopic, vision so important. With stereoscopic vision, we see exactly where our surroundings are in relation to our own bodies, usually with considerable precision. We are particularly good at spotting objects that are moving toward or away from us, and the positioning of our eyes means we can see partially around solid objects without needing to move our heads. It's easy to see why some people believe stereoscopic vision evolved as a means of survival.
Certainly, stereoscopic vision is vital for seemingly simple actions such as throwing, catching or hitting a ball, driving or parking a car, or even just threading a needle. That's not to say such tasks can't be managed without 3-D vision, but a lack of depth perception can make these everyday tasks much more complex.


The key to stereoscopic vision is depth, and our brain will happily take care of that for us, providing our eyes are given the right information in the first place. This is exactly how those red-and-blue glasses work -- each color filters out part of the image, giving each eye a slightly different view. The brain puts the two different images together, and those blue-and-red blurry images turned into a fantastic 3-D comic, or movie, or TV show. Stereograms, also known as Magic Eye pictures, use seemingly-random patterns of dots but rely on the viewer to cross his eyes in just the right way, or to look through the image until the eyes see just the right part and allow the brain to decode the hidden depth information.
Both methods have their disadvantages, of course -- the red-and-blue glasses make it difficult to show color in the 3-D image, and viewing stereograms is an art in itself. Neither method is entirely suitable for playing games.
Nevertheless, the underlying principle is exactly the same: creating and controlling those two different points of view. But just how easy is it to create these two separate images, one for each eye?
The answer is all about how games are created. Not so long ago, the graphics we saw on our computer screens were carefully drawn into the computer -- every single frame of animation, every different view of a character. If you wanted a dinosaur in your game, you sat down and drew the different views of a dinosaur into the computer.
Nowadays, games designers sit down with a 3-D graphics package and design their dinosaur in three dimensions. Once that's done, they needn't worry about the different views -- the computer has a 3-D model of the dinosaur in its memory, and the game simply works out where the player is looking and draws the correct view of the dinosaur using the 3-D model. In fact, everything you see on your screen in a modern 3-D game is produced the same way; the game is like a gigantic 3-D model. The computer works out what it needs to display on your screen and generates the appropriate view.
Since the computer is quite happy to create one point of view, there's no problem shifting the viewpoint slightly and creating another point of view. And after that, all you need is a way to get the correct image to the correct eye.


It's all down to the power of liquid crystal displays, or LCD. Just like the liquid crystal in a watch can be changed from transparent to black, the lenses of PC 3-D glasses can be transparent or opaque. In other words, the glasses can control which eye sees the image on the screen, and with careful timing you've got perfect 3-D. Here's how it happens:

1. The images are prepared by the computer and displayed.

Two images are generated, representing the views seen by each eye:
Both of these views are presented on the screen in rapid sequence:

2. While the left view is presented, the right eye is blocked by the LCD glasses. Similarly, when the right view is presented, the left eye is blocked.

All of this happens so quickly that the brain is entirely unaware of the two images merging together into a stereoscopic view. This is the same thing as when we watch a film using an old film projector and the sequence of still images flickering onto the screen merges together to form a movie.


So, we've seen that although there might be something complex going on behind the scenes, with the right equipment we can just sit back and let our eyes do the work. Of course, the technology wasn't always so simple; there have, in fact, been four generations leading up to today's 3-D glasses. The first generation modified the games themselves to make them compatible with stereoscopic 3-D. The games' creators had to specifically support each type of LCD glasses -- hardly an ideal situation. There was no guarantee that the glasses you'd bought would work with your favorite game. As you can imagine, that didn't appeal to many people; so a second solution was developed.
This second solution was to override the game, actually taking over the computer's screen and altering what was displayed. As far as the game was concerned, it was just doing what it normally did, except, of course, that some of the computer's time was taken up processing the image to make it 3-D. The result was slower performance and low-resolution, blocky images. It did work with hundreds of games, though, and that was a definite improvement.
The third generation worked in a similar way, modifying the graphics driver but also maintaining the resolution of the images -- no more blocky graphics! Unfortunately, it wasn't compatible with many games, though it was a definite forerunner to the 3-D glasses we have nowadays.
In the fourth-generation models, compatibility is high, the complicated work is done by the graphics card, and the lightweight LCD glasses flick so rapidly between the two images that all we see is crystal-clear, 3-D images.
So what's on the market? What should you look for? Let's find out...

Photo courtesy E-Dimensional Wireless E-D Glasses Components eDimensional, E-D and the eDimensional logos are registered trademarks of eDimensional, Inc. in the U.S. and other countries.

Although the basic technology is the same, there is a range of different glasses out there. You'll find lightweight, wireless glasses, as well as more basic (and therefore cheaper) pairs. The view through the glasses depends more on your computer's graphics card than the make of glasses, but you will find that different manufacturers offer extra software or other minor incentives. The lesson is: Shop around! If you get the chance to try a pair out before buying, don't hesitate -- try to imagine wearing them for an hour of intensive gaming. You might want to put in the extra money for a slightly better model. Bear in mind, too, that all glasses come with the standard video game warning concerning epilepsy, eye-strain and tiredness. If you generally find it difficult to cope with a standard flat monitor, you will definitely want to try out the glasses before you buy. Be wary also if you have an LCD flat-panel monitor, because current 3-D glasses don't work well with this kind of monitor. Be sure to check compatibility before you buy.
Check out exactly which kind of video card you have (manufacturer and model) and do a little bit of research before you make your purchase. The X-Force 3D Game Glasses, for example, will only work with nVidia video cards. Many glasses will work with various graphics cards, but the only way to tell for sure is to read the side of the box carefully.

Special thanks to Henry Wurst, Inc., the printer for How Stuff Works Express, for its help in creating this article.

The next time you read your favorite magazine or go through the latest catalog that arrives in your mailbox, stop for a moment and think about how that publication came to be. First, writers, editors and designers participate in the creative process. Printers take that creative work and turn it into the publications you read every day. Printing is a fascinating process involving huge high-speed machines, 2,000-pound rolls of paper, computers, metal plates, rubber blankets and sharp knives.

In this article, we'll look at offset lithography, the most commonly used printing process, and detail the three production steps: pre-press, press run and bindery. We'll follow the publication of our new magazine, How Stuff Works Express, from start to finish to explore this process.



­
Every print piece starts with the creative process. Writers, editors, graphic designers and artists are the initial step in the creation of magazines, newspapers, brochures, flyers, catalogs and other print pieces. The How Stuff Works Express creative team begins work months in advance of each edition's publication date. Topics for articles are identified and writers are assigned. Strict guidelines for word length and a reliance on custom graphics keep articles short, informative and entertaining. Editors help focus copy and keep the whole process moving.
Once the text has been developed, graphics are created. Nearly every illustration in How Stuff Works Express is developed as original art exclusively for the magazine. Many "e-meetings" between the author, illustrator and director of design move the work from conceptual drawings to final art.

Sample time machine concept drawing in pencil

Final color drawing

When each article is written, edited and approved with final art, the pieces are sent electronically to the director of graphic design for page layout. The director determines what page a story will appear on, where art will be in relation to words and, in some publications, where advertising will appear. Often, there are difficult decisions to make about how best to fit the pieces of art and text into very limited space. As in the making of a movie, some materials must be left on the "cutting room floor."

Digital "printer's file" of a How Stuff Works Express cover

Finally, after the layout of every page has been completed, edited and proofread, a digital "printer's file" is created for the entire document. This is usually done by burning a CD, but can also be done with Zip files or File Transfer Protocol (FTP).

There are nine main types of printing processes:

• offset lithography - what we are exploring in this article
• engraving - think fine stationery
• thermography - raised printing, used in stationery
• reprographics - copying and duplicating
• digital printing - limited now, but the technology is exploding
• letterpress - the original Guttenberg process (hardly done anymore)
• screen - used for T-shirts and billboards
• flexography - usually used on packaging, such as can labels
• gravure - used for huge runs of magazines and direct-mail catalogs

Offset lithography is the workhorse of printing. Almost every commercial printer does it. But the quality of the final product is often due to the guidance, expertise and equipment provided by the printer.
Offset lithography works on a very simple principle: ink and water don't mix. Images (words and art) are put on plates (see the next section for more on this), which are dampened first by water, then ink. The ink adheres to the image area, the water to the non-image area. Then the image is transferred to a rubber blanket, and from the rubber blanket to paper. That's why the process is called "offset" -- the image does not go directly to the paper from the plates, as it does in gravure printing.
Now, let's look at the steps in the printing process.


Before the job can be printed, the document must be converted to film and "plates." In the case of How Stuff Works Express, film negatives are created from digital files. Images from the negatives are transferred to printing plates in much the same way as photographs are developed. A measured amount of light is allowed to pass through the film negatives to expose the printing plate. When the plates are exposed to light, a chemical reaction occurs that allows an ink-receptive coating to be activated. This results in the transfer of the image from the negative to the plate.

Color negatives are "stripped" together for each page.

A blue-line print is made from "stripped-up" negatives and is used to check image position before printing.

There are different materials for plates, including paper (which produces a lower-quality product). The best plate material is aluminum, which is more costly.
Each of the primary colors -- black, cyan (blue), magenta (red), and yellow -- has a separate plate. Even though you see many, many colors in the finished product, only these four colors are used (you'll also hear this called the four-color printing process -- it's a little like the three-color process used in television).

The human eye blends four individual color dots into a single color.

We'll talk more about this later as we explore color and registration control.


The printing process used to print How Stuff Works Express is called web offset lithography. The paper is fed through the press as one continuous stream pulled from rolls of paper. Each roll can weigh as much as 2,000 pounds (1 ton). The paper is cut to size after printing. Offset lithography can also be done with pre-cut paper in sheetfed presses. Web presses print at very high speeds and use very large sheets of paper. Press speeds can reach up to 50,000 impressions per hour. An impression is equal to one full press sheet (38 inches x 22 and three-fourths inches), which is 12 pages of How Stuff Works Express.

Web-press paper-feed system showing the double roll of paper just before the splice from the smaller roll (on the bottom) to the larger roll. Each roll of paper weighs nearly 1 ton and is sufficient for 9,000 impressions (72,000 printed pages).

Even when a 1-ton roll of paper runs out, the presses do not stop rolling. Rolls can be spliced together as the web press is running by using festoons. Festoons are a series of rollers that extend up into a tower. A few moments prior to the splice occurring, the festoons will move up into the tower, pulling in large amounts of paper. At the moment the splice occurs, the rolls of paper stop rotating for a split second, at which point the paper is taped together automatically. As the newly spliced roll begins to pick up speed, the festoons begin to drop out of the tower at a rate predetermined by the speed at which the press is operating. The press operator never has to adjust the press controls during this operation.

Festoons are a series of rollers used to adjust tension before and after the splice from a small, fast-turning roll of paper to a large, slow-turning roll of paper.

The press has to maintain a constant balance between the force required to move the paper forward and the amount of backpressure (resistance) that allows the paper to remain tight and flat while traveling through the equipment.
The Inking Process
Ink and water do not mix -- this is the underlying principle of offset lithography. The ink is distributed to the plates through a series of rollers. On the press, the plates are dampened, first by water rollers, then ink rollers. The rollers distribute the ink from the ink fountain onto the plates.



The image area of the plate picks up ink from the ink rollers. The water rollers keep the ink off of the non-image areas of the plate. Each plate then transfers its image to a rubber blanket that in turn transfers the image to the paper. The plate itself does not actually touch the paper -- thus the term "offset" lithography. All of this occurs at an extremely high speed.

Close-up of rollers. The top series of rollers transfers the yellow ink to the rubber "blanket" cylinder (bottom roller), and then to the paper that is passing horizontally under the "blanket."

The paper is left slightly wet by all of the ink and water being applied. Obviously, there is a risk of the ink smudging. The smudging is avoided by having the paper pass through an oven. The oven is gas fired, and the temperature inside runs at 350 to 400 degrees Fahrenheit (176 to 206 degrees Celsius).

The paper is run through a long oven at about 375 degrees Fahrenheit (190 degrees Celsius). This dries (sets) the ink so it won't smudge.

Immediately after leaving the oven, the paper is run through a short series of large metal rollers that have refrigerated water flowing through them. These chill rollers cool the paper down instantly and set the ink into the paper. If this were not done, the ink would rub off on your fingers.
Color and Registration Control
Color and registration control is a process that is aided by the use of computers. Registration is the alignment of the printing plates as they apply their respective color portion of the image that is being printed. If the plates do not line up perfectly, the image will appear out of focus and the color will be wrong. A computer takes a video image of registration marks that have been placed on the press sheet. Each plate has its own individual mark. The computer reads each of these marks and makes adjustments to the position of each plate in order to achieve perfect alignment. All of this occurs many times per second while the press is running at full speed.

The RCS (Register Control System) provides constant adjustment of the press. The computer works in concert with a strobe light and video camera to constantly process information about color registration. Incredibly small adjustments, measured in the 1,000ths of inches, are automatically made to the color rollers to ensure proper registration.

Color control is a process that involves the way in which the ink blends together, and is tied closely to the plate registration. The amount of ink that is released into the units depends on how much ink is needed to achieve a desired look. The ink is adjusted via the control panel that is part of the overall control console. Prior to being placed on the press, the plates are scanned and the data is then transferred to a micro cassette. This serves as the "master" that directs the release of ink to pre-set values.

The web offset press that prints How Stuff Works Express is 115 feet long and weighs 500,000 lbs -- more than 150 Toyota Camrys! The process starts with a huge roll of paper that is fed through four banks of rollers. Each roller adds one color at a time, starting with black, then cyan (blue), magenta (red) and finally yellow.

Press speeds can run up to 50,000 impressions per hour.

Print quality is checked frequently by the press operator.

The bindery is where the printed product is completed. The huge rolls of now-printed paper are cut and put together so that the pages fall in the correct order. Pages are also bound together, by staples or glue, in this step of the process. In the case of How Stuff Works Express, a machine called a stitcher takes the folded printed paper (called press signatures) and collates them together. Then stitches (staples) are inserted into the signatures, binding them together.

The "stitcher" gathers, assembles and staples the magazines (called books) before they are sent for final trimming. This bank of 14 units can process about 9,000 books per hour!

The final components in the stitcher machine are the knives, which trim the paper to the final delivered size. The product is then ready to be shipped to the end destination.

Stereolithography, also known as 3-D layering or 3-D printing, allows you to create solid, plastic, three-dimensional (3-D) objects from CAD drawings in a matter of hours. Whether you are a mechanical engineer wanting to verify the fit of a part or an inventor looking to create a plastic prototype of an invention, stereolithography gives you a fast, easy way to turn CAD drawings into real objects. 3-D printing is a very good example of the age we live in. In the past, it could conceivably take months to prototype a part -- today you can do it hours. If you can dream up a product, you can hold a working model in your hands two days later! In this edition of How Stuff Works, we will take a tour of the stereolithography service bureau at PT CAM (Piedmont Triad Center for Advanced Manufacturing) so that you can understand everything involved and see some actual 3-D models that this technology has produced!

PT CAM uses a stereolithography machine produced by 3-D Systems and shown here:

3-D Systems stereolithography machine at PT CAM. See more pictures of stereolithography.

This machine has four important parts:

• A tank filled with several gallons of liquid photopolymer. The photopolymer is a clear, liquid plastic.
• A perforated platform immersed in the tank. The platform can move up and down in the tank as the printing process proceeds.
• An ultraviolet laser
• A computer that drives the laser and the platform

The photopolymer is sensitive to ultraviolet light, so when the laser touches the photopolymer, the polymer hardens.
If you stand next to the stereolithograph apparatus (SLA), you can actually see the laser as it builds each layer. This short MPEG file lets you see the laser building a small section of a model.

The basic printing process goes like this:

• You create a 3-D model of your object in a CAD program
• A piece of software chops your CAD model up into thin layers -- typically five to 10 layers/millimeter
• The 3-D printer's laser "paints" one of the layers, exposing the liquid plastic in the tank and hardening it
• The platform drops down into the tank a fraction of a millimeter and the laser paints the next layer
• This process repeats, layer by layer, until your model is complete

This is not a particularly quick process. Depending on the size and number of objects being created, the laser might take a minute or two for each layer. A typical run might take six to 12 hours. Runs over several days are possible for large objects (maximum size for the machine shown above is an object 10 inches (25 cm) in three dimensions).

A typical CAD drawing ready to be rendered on the 3-D printer. This particular piece is a plastic money clip that PT CAM gives away to visitors. Note the supports (in red) that separate the money clip from the tray and support it is it is being built. About 50 of these money clips can be created in a single run.

You start by creating a 3-D design for your object in a CAD program. This design is tweaked before building with supports that raise it up off the tray slightly and with any internal bracing that is required during building. The SLA then renders the object automatically (and unattended). When the process is complete, the SLA raises the platform and you end up with your 3-D object. If the object is small, you can produce several of them at the same time if you like. They all sit next to each other on the tray.

The platform in the tank of photopolymer at the beginning of a print run.

The following photo shows a tray after building is complete, with several identical objects that were produced simultaneously:

The platform at the end of a print run, shown here with several identical objects.

Once the run is complete, you rinse the objects with a solvent and then "bake" them in an ultraviolet oven that thoroughly cures the plastic.

The ultraviolet "oven" used to cure completed objects.

Stereolithography allows you to create almost any 3-D shape you can imagine. If you can get it into a CAD program, you can probably create it. The only caveat is the need for structural integrity during the building process. In some cases, you need to add internal bracing to a design so that it does not collapse during the printing or curing phases. The photo below shows you a typical object that has been created at PT CAM. The piece is lightweight and has the strength of polystyrene plastic. You can mount it, drill it, etc., so you can try it out in actual use. For example, a chair manufacturer will produce different arm rest shapes using stereolithography and try them out on actual chairs to see how they feel.
This is a close-up of an engine manifold:

For more detail on the manifold, see this short video.

Stereolithography is not an inexpensive process. The machines themselves usually cost in excess of $250,000. They have to be vented because of fumes created by the polymer and the solvents. The polymer itself is extremely expensive. CibaTool SL5170 resin, a common photopolymer used in stereolithography, typically costs about $800/gallon. For these reasons, it is uncommon to find stereolithography machines anywhere but in large companies. However, there are service bureaus that can make the advantages of stereolithography available to smaller shops and individuals. For example, PT CAM will do stereolithography for $55/hour, as well as allowing companies to purchase blocks of time for as low as $30/hour. That's not cheap, but compared to purchasing your own SLA and resin or having parts machined, it is a real bargain. You can e-mail your CAD design to PT CAM and, in many cases, get your parts shipped back to you in a day or two. The short cycle time is one of the most appealing things about stereolithography!
Special thanks to Joel Leonard, Jerry Watkins and Steve Oneyear for their help in creating this article!