Collision Course
Karen Moltenbrey
Issue: Volume: 26 Issue: 1 (Jan 2003)

Collision Course

It's hard to believe that it has been nearly four decades since the television show Star Trek, now a science-fiction phenomenon, was first beamed into our living rooms. Over the years, Star Trek fans have been treated to several incarnations of the original TV series, nine feature films, an animated television series, a Star Trek theme park, and more conventions than even the most faithful fan would care to count. From the mid-1960s to the present, the starship Enterprise has been damaged, retrofitted, destroyed, and restored several times over—each incident more incredible than the other. In the newest film, Star Trek: Nemesis, the effects artists boldly venture "where no one has gone before," using photorealistic computer graphics to create a spectacular crash involving the Enterprise and an enemy ship.

In Nemesis, the tenth film in the Star Trek franchise, Captain Picard and his crew are diverted from their destination—a wedding on the planet Betazed—to negotiate a peace treaty with their longstanding foes, the Romulans. After arriving on Romulus, the group is faced with a powerful new weapon that could destroy the Enterprise, and the Earth, while Picard meets his most dangerous adversary yet—a surprisingly personal nemesis built in his own image.

To support the Nemesis story line, Digital Domain contributed more than 400 photorealistic effects shots that are virtually invisible because they are so closely integrated into the scenes (see "Backdrop," pg. 40). Some involve the standard Star Trek visuals—weapon fire, transporter effects, star fields, and explosions—in addition to a new, sleeker version of the Enterprise, the menacing Reman Scimitar warship, and small enemy craft. The most compelling effects, though, are contained in an enormous battle scene that culminates in an elaborate explosion after Picard makes a desperate decision to ram the Reman ship.

As they did for the external shots in the crash sequences, Digital Domain artists achieved a greater level of authenticity by using both CG and practical elements for this interior shot.

For moviegoers, the scene is one of the most exciting that Star Trek fans have witnessed. For Digital Domain, it is one of the studio's more complicated to date, requiring an extremely complex integration of practical and CG elements. Not only did the transition from the real to the virtual have to be transparent to viewers, but the image quality had to be exceptionally realistic, thereby lending believability to the futuristic plot. The key to achieving those goals was to replicate the textures, lighting, and cinematography used on the practical set and apply them to the virtual imagery.

Before the artists could create the climactic scene, they first had to construct, then replicate, the spaceship models that would be used in other shots throughout the film. Despite the existence of numerous digital Enterprise models from previous Star Trek productions, Digital Domain crafted a new, improved version of the Federation ship, using a 12-foot practical model from some of the more recent films as a reference for lighting and scaling its 3D version. The group also received sketches and artwork from John Eaves, the Star Trek Productions illustrator responsible for most of the ship designs in the film. Those drawings reflected his vision for the modified Enterprise as well as for the other spacecraft in the film.

Using NewTek's LightWave, the artists constructed the digital spacecraft as well as the ship extensions that would be combined with the practical models, constantly refining the geometry as they received updated sketches from Eaves. For texturing, including the addition of subtle wear and tear, the team used Adobe Systems' Photoshop and Illustrator. "Our scenes [of the all-digital ships] are very large in scope, from miles away to within a few feet, sometimes within a single shot," says Jay Barton, team lead for the ship construction. "Because of these [extremely close-up] 'paint-scraper' shots, the models had to be incredibly detailed to hold up on screen." To illustrate how robust the models are, he notes that the completed Enterprise model consists of 1.3 million polygons—the heaviest digital version to date—while the larger Scimitar sports 1.5 million polygons, and each of the two Romulan War Birds contains 1.1 million polygons.

Approximately 50 percent of the film takes place inside the nebulous Rift area, which was created as an all-3D environment inside Houdini. To economize the graphics in the Rift scenes, the artists didn't pre-render the Rift or star fields. Instead, th

According to visual effects supervisor Mark Forker, director Stuart Baird wanted the movie to have a darker, more dangerous feel than previous iterations of the property. "In this film, space is darker, the ships are darker, everything is darker," he says. For instance, the black, metallic-like surface of the Scimitar projects a cold and ominous presence, while the sleek, streamlined redesign of the Romulan War Birds gives them a menacing, bird-of-prey appearance, including feather-like paneling.

These high-resolution spaceship models are indeed more realistic than their predecessors. But their appearance was not enough to overcome the challenges required during one of the most complex sequences in the film—a 60-shot World War II-style dogfight among the Enterprise, Scimitar, and the two War Birds that ends when the Enterprise crashes head-on into the Scimitar. Forker felt that the best way to accurately portray the violent collision and the devastating aftermath would be to combine practical miniature models with precisely matched CG ship extensions.

"Compared to previous projects, the process of integrating the extensions for the crash sequence was completely transparent to the workflow," says Markus Kurtz, CG supervisor. "The integration team tracked the plates, and the model and lighting team matched the CG models seamlessly to the miniatures. The two pieces fit together with little manipulation compared to what we went through previously." Kurtz and Forker also credit Digital Domain's updated production pipeline, which enabled the team to exchange data among various software packages, streamlining what used to be a difficult task.

For the practical portion of the collision, Digital Domain created what it describes as one of its most complex miniature setups yet. "We pre-visualized the collision using [Side Effects Software's] Houdini, which enabled us to determine variables such as the scale of the miniatures and the speed of the collision," explains Kelly Port, associate visual effects supervisor. Digital Domain's model shop then built a small portion of the Enterprise's saucer section for the crash, which at one-fiftieth scale was approximately 17 feet wide. The Scimitar's front section was just as big, giving an appropriate scale to the destruction. Once the models were ready, they were rigged upside down so the debris would fall "up" to simulate zero gravity.

The physical Enterprise saucer was then rigged on a dolly and connected to a high-powered winch that pulled it into the Scimitar at about 20 mph. Because the cameras were running at 360 frames per second, an enormous amount of light was required—approximately 84,000 watts. Once the plates were shot and edited together, Digital Domain used its proprietary tracking software, Track, to integrate the miniatures and the CG ships into the same 3D space so that they could properly extend both ships and add debris.

Alas, not every fragment that broke off during the crash fell into space exactly as Forker wished. In those instances, the team either used luminance keys or Avid Technology's Elastic Reality to remove the wayward physical particles. To further enhance the physical crash and to provide an accurate sense of scale, the artists used Nuke, Digital Domain's own compositing software, in addition to Discreet's Flint, Flame, and Inferno, to add a plethora of CG debris generated in Houdini.

Orchestrating the physical setup was only half the battle; the artists still had to add precisely matched CG extensions onto the physical ship models. Both types of models were generated synchronously, to ensure that in the end they aligned perfectly. Once the models were completed, the artists used Illustrator and Photoshop to replicate the weathered surface of the miniatures on the digital versions.

According to Forker, lighting played an equally important role in the integration of the digital and practical objects. Using LightWave, the artists digitally replicated the lighting environment from the practical shoot, so the different ship surfaces would look as if they were reacting to the same light sources. Further complicating this task was the fact that the explosive effects—a by-product of all the weapon fire—were both practical and CG elements, the latter of which were generated in Houdini. "We had to be careful when adding the interactive lighting to the CG ship extensions in order to marry the CG and practical lighting elements and have it look believable," Forker says.
Digital Domain's robust production pipeline enabled the team to choose the most appropriate tool for each effect. For instance, the CG ships shown here were modeled and lit in LightWave, animated in Houdini, and textured in Photoshop, while the character

Another challenge to lighting this sequence was the fact that it takes place within a greenish nebulous environment called the Rift—a familiar Star Trek convention used to sever communication between the Enterprise and the Federation. Similar cloud-like environments have appeared in previous films as 2D matte paintings. In Nemesis, the 3D Rift effect was produced by using a volumetric shader in Houdini, which was then output as a high-resolution environment map that was applied in Nuke to an environmental sphere. Nuke would figure out what area of the Rift was seen in each shot, based on the camera position and rotation.

The final piece of the integration puzzle was to enhance the photorealistic aspect of the digital elements by applying as many cinematographic attributes as possible. To that end, the group replicated the distortion characteristics of the camera lens used for filming the battle sequence and applied them to the CG imagery. "Every studio uses compositing techniques such as lens flares or adding grain to the shot, but only a few apply lens distortion," notes Forker. That's because figuring out the characteristics of lenses is very time-consuming, involving numerous test shots and elaborate analysis. Using each camera lens, the Digital Domain group conducts test shots of a specific grid pattern that is projected onto a wall. By comparing the original pattern with the pattern captured on film, the team is able to determine the amount of distortion produced by each lens. "Over the past few years, we established a fairly sophisticated pipeline for just analyzing lenses," says Kurtz.

Furthermore, the entire film production was done in Cineon color space, meaning the luminance values are far greater than 1, as opposed to video space (8-bit color), where each image is limited to values between 0 and 1. "In Cineon, more detail is present in the highlights, which helps make the CG look more photographic," says Kurtz.

Like the visual effects specialists who have gone before them, Digital Domain has continued to raise the bar when it comes to Star Trek films, creating bigger, better, and more of just about every type of effect. By building robust digital models and using various digital techniques to blend them seamlessly into the live action, the artists have created the most authentic atmosphere yet for a Star Trek property, breathing a whole new life into the decades-old franchise. ..

Karen Moltenbrey is a senior editor for Computer Graphics World.

Images © 2002 Paramount. Courtesy of Digital Domain.

In a startling moment near the beginning of the film, a mysterious but deadly weapon is deployed in the Romulan senate, shooting a green beam of light toward the ceiling. The beam, which is used in 32 shots throughout the film, was generated with volumetric lighting augmented with particles inside Houdini.

Soon after the weapon is activated, the senators are showered with deadly particles, which reduce them to ashes. The camera focuses on the Praetor (leader) as he twists in pain while his skin begins to burn. Then, he falls to his knees as his condition worsens, and, finally, collapses to the floor and turns to dust.

To simulate the effect, Digital Domain generated head scans of all the actors in the scene. For the Praetor, who appeared in the close-ups, Gentle Giant Studios used a Cyberware scanner to create a high-density file, while the minor actors were digitized using Eyetronics' portable scanner. Next, the artists built subdivision models using Cyberware's CySlice conversion software for matching and tracking. Later, they imported the geometry into Alias|Wavefront's Maya for animation. The final animation was transferred into Houdini, where effects artists applied the face decay. For the final shot, when the character turns to ash, the digital effects are suspended, and a prop is used. —KM

The enemy makes a deadly statement early in the film by deploying a smaller version of its new weapon of mass destruction, thereby turning the Romulan senators to dust.

Adobe Systems
Avid Technology
Side Effects Software