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For those of you who have not yet gotten your hands on Ron Brinkmann’s second edition of his amazing book, The Art and Science of Digital Compositing, we have a few sneak peeks of chapter one. Sit back and feed your mind!

Click here to visit the book’s official site.

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Introduction To Digital Compositing.

An alien spacecraft hovers over New York, throwing the entire city into shadow. Massive armies converge on a battlefi eld. A giant ape faces off against a Tyrannosaurus Rex. And the Titanic, submerged for decades, sails once more.

Usually the credit for these fantastic visuals is given to “ CGI ” (computer-generated imagery) or “ computer graphics, ” an attribution that not only broadly simplifi es the technology used but also ignores the sizeable crew of talented artists who actually created the work. Computer graphics techniques, in conjunction with a myriad of other disciplines, are commonly used for the creation of visual effects in feature fi lms. But the term “ computer graphics ” is broad and covers a wide variety of methods that rely on a computer to help produce images. Many of these methods are merely traditional methods that have been updated to take advantage of modern tools. In fact, even the typesetting of a book like this is now almost completely done using a computer, and as such this page could loosely be considered a piece of “ computer graphics. ”

When dealing with computer graphics as used for the creation and manipulation of images, we will usually break the subject down into two primary subcategories: 3D graphics 1 and 2D graphics . The names indicate whether the work is considered primarily three-dimensional in nature, or two-dimensional. The fi rst category, the “ 3D ” work, involves creating a complete model of an object within the computer. This model can be viewed from any angle, can be positioned relative to an imaginary camera, and can generally be manipulated as if it were a real object, yet it exists only within the computer. Even though the way we are interacting with the object is still based on a two-dimensional display device (the computer ’ s monitor), the model itself is a mathematical simulation of a true three-dimensional object. This model can be lit,
textured, and given the ability to move and change. Once a particular camera view is chosen and the color, lighting, and animation are acceptable, special software will render the scene to produce a sequence of images.

While the 3D aspect of visual effects seems to get a great deal of recognition, it is only one piece of the puzzle that makes up a fi nished shot. The other half of the visual effects process involves working with preexisting images, manipulating and combining them to produce new images. These images can be from just about any source, including rendered images produced by the 3D process. This process of manipulating
existing images is identifi ed as being “ 2D ” work because of the fl at, two-dimensional images with which it deals and because there is essentially no attempt to introduce any three-dimensional data into the process. Not every film that makes use of visual effects will include 3D work, but any time there is a visual effect in a film, you can assume that 2D work was done. It is the backbone of visual effects work, and the
final, most important step in the creation of the desired imagery.

Even with a fully rendered 3D movie like Pixar ’s The Incredibles , 2D effects and tools are used to enhance and integrate the rendered 3D images. 2D manipulations have historically been accomplished via a number of different methods, as we’ll discuss in a moment. But these days, most 2D work is done with the aid of computers, and the bulk of this 2D work is classified as digital compositing.

Definition

Digital compositing, as we are going to be discussing it, deals with the process of integrating images from multiple sources into a single, seamless whole. While many of these techniques apply to still images, we will be looking at tools and methods that are useful and reasonable for large sequences of images as well. Before we go any further, let’s come up with a specifi c defi nition for what this book is all about.

Digital Compositing: The digitally manipulated combination of at least two source images to produce an integrated result.

By far the most difficult part of this digital compositing process is producing the integrated result—an image that doesn’t betray that its creation was owed to multiple source elements. In particular, we are usually attempting to produce (sequences of) images that could have been believably photographed without the use of any postprocessing. Colloquially, they should look “ real. ” Even if the elements in the scene are obviously not real (huge talking insects standing atop a giant peach, for example), one must be able to believe that everything in the scene was photographed at the same time, by the same camera.

Although so far we ’ ve mentioned only a few big-budget examples of digital compositing being put to use, in reality you ’ ll find digital compositing at work just about anywhere you look in today’s world of media and advertising. Pull a magazine off the shelf and in all likelihood you will find that most of the art and graphics have been put together using some sort of computerized paint or image-editing program. Television commercials are more likely than not to have been composited together from multiple sources. Yet whether the digital compositing process is used for a business presentation or for feature-film special effects, the techniques and tools employed all follow the same basic principles.

This book is intended to be an overview that will be useful to anyone who uses digital compositing. However, you will probably notice that many topics, descriptions, and examples seem to approach the subject from the perspective of someone working to produce visual effects for feature films. This emphasis is not only due to the author’s experience in this field, but also because feature-film work tends to push the limits of the process in terms of techniques, technology, and budgets. Consequently, it is an ideal framework to use in providing an overview of the subject. Additionally, it allows for the use of examples and sample images that are already familiar to most readers.

The title of this book, The Art and Science of Digital Compositing, was coined to stress the fact that true mastery of digital compositing includes both technical and artistic skills. As with any art form, the artist must certainly have a good amount of technical proficiency with the tools that will be used. These tools could potentially include any number of different hardware and software compositing systems. But one should also become knowledgeable about the science of the entire compositing process, not just specific tools. This would include everything from an understanding of the way that visual data is represented in a digital format to knowledge of how a camera reacts to light and color. Please remember, though, that all these technical considerations are simply factors to weigh when confronted with the question of “ Does it look right? ” The answer will ultimately be a subjective judgment, and a good compositor who is able to consistently make the decisions that produce quality images will always be in high demand.

The combination of multiple sources to produce a new image is certainly nothing new, and was being done long before computers entered the picture (pardon the pun). Although this book is about digital compositing, let’s spend a moment looking at the foundations upon which digital compositing is built.

Historical Perspective

In the summer of 1857, the Swedish-born photographer Oscar G. Rejlander set out to create what would prove to be the most technically complicated photograph that had ever been produced. Working at his studio in England, Rejlander selectively combined the imagery from 32 different glass negatives to produce a single, massive print. A reproduction of this print, which was titled The Two Ways of Life , is shown to the left. It is one of the earliest examples of what came to be known as a “ combination print. ” (Photo courtesy of the Royal Photographic Society Collection, Bath, England. Web site www.rps.org.)

Had the artist wished to capture this image on a single negative, he would have required a huge studio and many models. Even then, it is doubtful whether he could have lit the scene with as much precision or have positioned all the people in exactly the fashion he desired. Certainly it could have proven to be an expensive,
time-consuming process. Instead, he painstakingly shot small groups of people and sets, adjusting each for the position and size that he would need them to be. In some cases, the only way to make them small enough in frame was to photograph them reflected in a mirror. Once the various negatives were created, the combination process involved selectively uncovering only a portion of the printing paper and exposing
the desired negative to that area.

The scene that resulted from this complex undertaking was designed to depict the two paths that one may choose in life. The right side of the image represents the righteous path, with individual figures who illustrate Religion, Knowledge, Mercy, Married Life, and so on. The left side of the image depicts somewhat less lofty goals, with figures representing everything from Idleness to Gambling to Licentiousness to Murder.

Photography was only just becoming accepted as a true art form, but Rejlander’s work was immediately recognized as an attempt at something more than the typical documentary or narrative photographs of the time. This is important to understand, since it points out that Rejlander used this combination technique in pursuit of a specific vision, not as a gimmick. There was a great deal of science involved, but more important, a great deal of art.

While The Two Ways of Life received quite a bit of recognition, it was also the subject of some controversy. Although part of this had to do with its subject matter (a Scottish exhibition of the work actually hung a drape over the nudity-rich left half of the image), the issue of whether or not such “ trick ” photography was ethical or artistically valid was continually raised. Eventually Rejlander himself denounced the practice, stating,

I am tired of photography for the public—particularly composite photographs, for there can be no gain , and there is no honour, but cavil and misinterpretation.

Fortunately, the techniques continued to be used and refined even without Rejlander’s support, and few people today consider compositing (at least conceptually) to be particularly dishonorable.

Motion picture photography came about in the late 1800s, and the desire to be able to continue this sort of image combination drove the development of specialized hardware to expedite the process. Optical printers were built that could selectively combine multiple pieces of film, and optical compositing was born. Many of the techniques and skills developed by optical compositors are directly applicable to the digital realm, and in many cases, certain digital tools can trace not only their conceptual origin but also their basic algorithms directly to optical methodologies. Consequently, the digital compositing artist would be well served by researching the optical compositing process in addition to seeking out information on digital methods.

A number of early examples of optical compositing can be found in the 1933 film King Kong. The image shown above is actually a composite image that was created in the following fashion: The giant ape was photographed first—a 16-inch tall miniature that was animated using stop-motion techniques. This process involves photographing the model one frame at a time, changing the pose or position of the character between each frame. The result, when played back at normal speed, is a continuously animating object. After this footage was developed and processed, it was projected onto a large rear projection screen that was positioned on a full-sized stage. The foreground action (the actress in the tree) was then photographed while the background footage was being projected behind it, producing a composite image.
This particular type of compositing is known as an in-camera effect, since there was no additional postproduction work needed to complete the shot. Other scenes in the film were accomplished using an early form of bluescreen photography (which we will discuss further in Chapters 6 and 12), where the foreground and background were photographed separately and then later combined in an optical printing step.

Nowadays, optical compositing has effectively been replaced with general-purpose computer systems and some highly specialized software, but the concepts have not really changed.

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Have we gotten your attention? great! we will post the continuation of this “introduction to digital compositing” in a few days.. while you take time to digest and maybe even run out to get this great resource book!