Issue: Volume: 26 Issue: 4 (April 2003)

Pyramid Scheme

By Karen Moltenbrey

The Great Pyramid of Giza, the burial place of King Khufu, was constructed more than 4500 years ago, yet its craftsmanship makes it one of the most impressive structures ever built. This architectural marvel, the only one of the Seven Wonders of the World that has survived, spans 13 acres and, when built, rose more than 480 feet and contained 2.3 million blocks of stone, each weighing an average of 2.5 tons. Moreover, the pyramid—whose sides are geometrically precise to within two inches—aligns with the four points of the compass almost perfectly.

Today, people still gaze in amazement at the magnitude and beauty of the Great Pyramid, wondering how it was built. A widely held belief is that hundreds of thousands of slaves constructed the temple. This notion, thought to have originated 2000 years ago with the Greek historian Herodotus, persists even today, thanks in part to films such as The Ten Commandments. Archaeologists and other experts, however, have uncovered evidence suggesting that conscripted labor was used to build the structure. Using state-of-the-art computer graphics to illustrate these research findings, the BBC has created Pyramid, an hour-long documentary/drama that focuses on this massive construction project from the point of view of the laborers.

The artists created this camera shot, which looks down on the construction site, to show the true scale of the Great Pyramid and its related structures. Images courtesy Mill TV.

Although the story is told through the eyes of a fictional young Egyptian conscript, Nakht, the facts depicted in the program—which covers the entire project, from the workmen's journey down the Nile toward Giza to the actual building of the structure—are based on scientific evidence. "Nakht's story provides a powerful emotional focus, enabling the viewer to engage directly with the past," says Pyramid producer/.director Jonathan Stamp. "We learn of the hardships and the great dangers of the pyramid builders' world, and also of the comradeship. By the time we arrive at the end of Nakht's story, we understand the pyramid as never before."

The program—which aired in the US last month on the Discovery Channel with the reworked title Building the Great Pyramid—combines photorealistic digital elements and effects created by Mill TV with live-action footage shot on location. All told, nearly half the shots in Pyramid contain some type of CGI. "We created huge architectural and crowd scenes, and provided an immense but historically accurate environment," says Dave Throssell, head of Mill TV in London. "The vision for the effects was to make them invisible to the viewer."

According to Mill TV's Angela Hunt, Pyramid's visual effects supervisor, the directive was to re-create the temple's construction on a massive scale by using small practical sets and only 30 actors. "Our aim was to achieve this through photorealistic visual effects," she says, "which is unusual for a documentary."

Nearly half the shots in the television production Pyramid are augmented with photorealistic digital imagery, from digital actors to this 3D pyramid. Pyramid, a BBC/Discovery Channel/NDR Germany/TBS Japan co-production.

Pyramid incorporates an extensive amount of digital elements for generating crowds of workers, creating compelling backgrounds, and showing the edifice throughout the various stages of construction. A 3D CG pyramid was even used in the sequences containing the completed structure, showing the temple in a pristine state once the workers smoothed the rough surface and added the white limestone shell finish. "Even the ground (sand) is computer generated," says Hunt. "At first, I hesitated over that, hoping we would get some aerial shots over which we could place our CG—just so we would have some real elements in the sequences. However, we were unable to get permission to fly a helicopter above the area, so we had to re-create the environment within the computer."

As with all the digital imagery, the virtual pyramid as well as the ancillary buildings were modeled in Softimage's XSI, textured in Adobe Systems' Photoshop, and rendered in Mental Images' Mental Ray embedded in XSI. In most instances, the team used photographic textures, acquired from high-resolution stills that Hunt shot while on location in Egypt to ensure that the live action was being filmed in accordance with the previsualization created by Mill TV. "We knew which types of surfaces we needed—rough and polished limestone, mud bricks, and so on—for our models and matte paintings," she adds. The group also conducted an effects shoot, filming dust and smoke elements against a black backdrop. The artists later inserted these live-action effects into the various scenes containing CG models, making them appear more authentic.

The team then built the digital pyramid brick by brick, just like the Egyptians did years before, only this time using digital blocks. To make the structure look natural, the artists modeled each of the blocks individually, varying the look slightly. For added realism, the technical department at Mill TV wrote a script within Softimage|XSI that "aged" the bricks in each layer to coincide with the natural weathering effects that would have occurred during the actual structure's quarter-century construction cycle. According to technical director Adrian Wyer, the group saved at least three weeks worth of work by automating this process.

For this shot along the Nile, the team at Mill TV added a computer-generated pyramid and embankment in the background, and painted out present-day artifacts.

Whereas the artists easily calculated some measurements—such as those for the CG pyramid—from existing geometry, others required educated opinions from archaeologists and Egyptologists. Such was the case with the ramps used to haul the massive blocks of stone onto each subsequent layer. Archaeological remains at the site show that the ramps existed, but their exact dimensions are unknown.

"No one knows how far back into the desert the ramps extended," says Hunt. "But when we created our model with one main ramp reaching to the top of the pyramid, we found that for it to be practical, it would have had to stretch into the desert for more than 2 miles. This would have made the ramp construction a much larger project than the pyramid construction." Based on those results, the artists and experts agreed that in all likelihood the Egyptians built a main ramp from the quarry up to about a third of the height of the pyramid. Then they built a series of spiral ramps around the structure's perimeter, resulting in a manageable incline for the workers to use.

Experts believe that approximately 20,000 people used the ramps to build the Great Pyramid. For the modern-day Pyramid production, however, only 30 real-life "laborers" were available. The remaining workforce was digital. Yet, these CG characters had to seamlessly blend into a scene with their live coworkers to maintain the illusion of reality. "We used various tricks to create the workforce, from postproduction replication of the live actors to the all-CG teams," says Hunt. "The construction site is a big area, and we had to fill it with workers so the scale of the building process would be apparent."

To illustrate the massive scale of the construction project, the artists populated scenes with digital actors, many of whom were modeled and animated in Softimage|XSI.

To enhance the realism of these digital characters, the team applied photographic textures to the models, then varied their physical appearances by making some heavier or taller, for example. "This process was made easier by the fact that the Egyptians looked similar in that they all had dark hair and dressed similarly in white loin cloths," says Hunt. Next, the group animated the models using data acquired from mocap studio Centroid 3D with a Motion Analysis optical motion-capture system and processed with Kaydara's MotionBuilder. The animators then imported the data into Softimage XSI, using the software's RTK module for animating the crowds and the animation mixer feature for editing the large amount of motion data and applying it to the characters.

"We gave all the characters distinct tasks, just as they would have had in reality long ago," Hunt says. This was done through a Web-based system, with which the group positioned the characters by dragging and dropping "teams" of digital actors into an area of a scene. Before this could happen, the characters and their actions were randomized in two stages. During the setup of teams (containing a maximum of 20 characters), animation director Jordi Bares modified the motion-capture information using XSI's animation mixer. Once the artists placed the characters in a scene, they further randomized the timing of the models' actions and gait using a customized script.

In one particular sequence, 30 extras were filmed along the bank of the Nile River as they waited for a boat to dock. After reviewing the scene, Stamp determined that more people should be added to the mid-range shot, so the digital artists included 30 digital actors as well. "Despite the close proximity of the camera and having to composite CG characters next to real extras, it's difficult to make the distinction between what is real and what is virtual," Hunt notes. For tracking the scene, the team used Science-D-Vision's 3D-Equalizer and 2d3's boujou software.

To re-create the Giza Plateau as it may have looked thousands of years ago required a great deal of work on the part of today's digital architects. Although Pyramid's scenes were all shot outdoors in the Egyptian desert, numerous touch-ups, rotoscoping, and even entire matte paintings were necessary to maintain a historical look. "There are telegraph poles, tourists dressed in modern clothes, and other evidence of the present day all around the area," says Hunt. "In fact, we did very little shooting on the plateau. Instead, we shot those areas with locked-off plates [instead of more expensive motion cameras], which were tiled together so we could do a post pan [camera move] over the area.

"Throughout the project, we had to keep asking ourselves, what is going to make this scene look real?" Hunt continues, "Sometimes it was just a matter of adding some distance between the main objects in the foreground and those in the background of a matte painting, or adding heat haze, blowing dust, or smoke to give some movement to an otherwise static frame."

Two of the more complex scenes in the program involved wide live-action shots of boats floating down the Nile. According to Hunt, the director wanted to illustrate the importance of the waterway as the ancient region's main form of transportation. So, the production team constructed a boat similar to those used during the period, and filmed various plates with a camera as it was piloted up and down the river. The props department "dressed" it differently for each plate using pots, animal feed, and canopies. When the boat headed south, it was sailed; when it headed north, it was rowed—as shown in ancient hieroglyphic texts. During postproduction, the artists rotoscoped all the masts, riggings, sails, and people from each shot using Discreet's combustion, then composited the elements with Discreet's flame to achieve a "busy" looking river.

In another sequence shot along the Nile—this one showing the Pharaoh's body being carried from the funeral barge—the team used a different approach. Initially, the production group built a large set piece along the river, planning to film the set and the actors. "But it got late and the sun was on the opposite side of the set piece, so the entire area was bathed in darkness," says Hunt. "As a result, we created the entire set in CG—even the actors were digital."

To create water traffic, the crew filmed a boat as it sailed down the river (above), then rotoscoped elements and composited them into the final shot (below).

According to Hunt, no one "trick" enabled the team to achieve its goal of photorealism for Pyramid. Rather, it was a matter of combining numerous techniques. "In some shots, we created the entire scene from scratch," she notes. "In other instances, we augmented the shot with composited live-action or CG elements."

In the end, completing the work on the docudrama required just as much ingenuity—though not as much hard labor—as building the original pyramid.

Karen Moltenbrey is a senior editor for Computer Graphics World.

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