Ghost Effects
Martin McEachern
Issue: Volume: 32 Issue: 7 (July 2009)

Ghost Effects

Terminal Reality and Atari catch the spirit of the iconic 1980s classic film

Strap on your proton pack, check your PKE meter, and be careful not to cross the streams as you take your place beside Bill Murray, Dan Aykroyd, Harold Ramis, and Ernie Hudson in battling an ectoplasmic threat of Gozerian proportions in one of the most highly anticipated sequels of recent years.

The artists at Terminal Reality proved they weren't afraid of any ghosts, re-creating the campy appeal of the Ghostbusters movies for a game title.

Terminal Reality’s Ghostbusters: The Video Game reunites almost all the principal cast members from the eponymous 1984 comedy classic and transports them back to 1991 for a new adventure. From script development to design, the game marks an unprecedented effort from an original cast, including William Atherton as Walter Peck, the city employee still at odds with our heroes, and Annie Potts as Janine, the Ghostbusters’ secretary. They’re joined this time by new cast members Brian Doyle-Murray, playing Jock Mulligan, the new mayor of New York City, and Alyssa Milano, playing the new love interest, Dr. Illyssa Selwyn.

Artists developed a head-sculpting rig within Autodesk's Maya called Adam and Eve which helped them model and light the character, including ghostbuster Winston Zeddemore (above)

Capitalizing on this cast, the game features actor-specific facial animation and smooth, mocapped performances that perfectly capture the chemistry between the oddball characters. It also contains fully destructible and incredibly realistic New York City sets, along with physics, slime, and real-time dynamic lighting effects that are out of this world—thanks in part to Terminal Reality’s newly revamped Infernal Engine, which the company is positioning as a competitor to the Epic Unreal 3 engine. While the engine has been in use since BloodRayne in 2002, it underwent a massive upgrade for the PlayStation 3 and Xbox 360. Ghostbusters is the first Infernal Engine title that will ship for current platforms. Meanwhile, Red Fly Studio is also using the engine to bring the title to the Wii, PS2, and DS.

Past Issues

Despite the high caliber of talent and technology, the game followed a very long and rocky road to release that began in 2006, when Slovenian developer Zoot­fly began production on an unlicensed Ghostbusters game. Although unable to secure the rights from Sony, the developer released videos of the game on the Internet that garnered an overwhelmingly positive reaction, so much so that now-defunct Sierra Entertainment was able to convince Sony that Ghostbusters was still a thriving marquee franchise (a Ghostbusters III movie is planned for 2012 release). Given the green light, Sierra hired Terminal Reality to develop the game after seeing a demonstration of the physics capabilities of the new Infernal Engine.

In 2007, Terminal Reality—armed with a script from Ramis and Aykroyd, and star power galore—began development. But a year later, when Vivendi merged with Activision, the newly formed Activision Blizzard (the publisher of Sierra’s titles) announced it would only release five franchises. Ghostbusters would not be one of them, and development was suddenly halted. The newly privatized Atari saw potential and, believing the ghost chasers could still capture and contain the imaginations of a whole new generation, stepped in and escorted it to its release last month.

Each ghostbuster, includin Ray Stanz (Dan Aykroyd), is built with approximately 31,000 triangles to resemble the real-life actor who assumed that movie role. at left is the wireframe view of the Stantz game character, and right shows the viewport render of the character.

Set two years after the events of Ghostbusters II, players assume the role of a new recruit hired to test Egon Spengler (Ramis) and Ray Stantz’s (Aykroyd) new experimental equipment during a rise in paranormal activity. Ramis and Aykroyd crafted a new story that revisits all the key locations, spectral hot spots, and happenings from the original films, providing closure and texture for many unresolved plot points and characters, while still expanding the tale and deepening the characters. Rooting the game in the soil of the old films “was something we all wanted to do from the beginning,” says creative director Drew Haworth. “Since a true Ghostbusters game hasn’t been made in a while (some would say ‘ever’), we wanted people to know this really was 100 percent the real deal. People needed to see what they know about Ghostbusters, what the characters looked like then, not 20 years later.”

Interactive Storytelling

While both Ramis and Aykroyd are accomplished writers, interactive story­telling was virgin territory for both, and thus they took a much looser approach to hammering out the script, collaborating with Terminal Reality, laying out the plot points, and fleshing out the characters, while the team helped them through the gameplay elements.

“A lot of the interactive aspect was new to them, particularly the length of the script required to cover four major speaking roles in a wide variety of possible actions and reactions,” says Haworth. “They’re used to 120-page movie scripts, and the game ended up right around 10,000 spoken lines, not counting all the lines that were recorded but not used.” In return, the two writers/actors provided crucial input, such as the ideal New York City locations for missions and scenes, and how the science behind the equipment—and the equipment, itself—works. They also helped the developer stay consistent with the Ghostbusters canon, providing, along with the script, little bits of insight into the speech habits and idiosyncrasies of each character’s personality.

Reuniting the original Ghostbusters cast would have been a waste of time if Terminal Reality couldn’t capture their likenesses. Making the task harder, the actors had to be “de-aged” by almost 20 years, to appear as they would have in 1991. Hence, scanning was out of the question. Instead, the team developed a head-sculpting rig in Autodesk’s Maya called Adam and Eve. “We first modeled and UV’d generically proportioned male and female heads. We paid attention to the poly count as well as the edge flow so each head could animate properly,” says lead animator Angel Gonzalez. “We then put joints in the head at specific points so we could get some interesting shapes.”

Next, the team grabbed screen shots of the actors from films circa 1991 and imported them into Maya. “Since the images come from many angles, we needed to create a camera system in Maya that allowed the modelers to switch quickly between them to check their modeling progress,” explains Gonzalez. “Since it’s hard to get a perfect orthographic (front and profile) view for any actor—most of them have a preferred ‘good’ side—we would end up with as many as six to 10 cameras on some heads.” The modelers would use all those camera angles to start the sculpting process.

The modelers also used a front projection map on each camera’s image plane to measure the fidelity of their digital doppelganger’s face. Once the models were finished, artists imported them into Adobe’s Photoshop, Autodesk’s Mudbox, and the Infernal Engine to complete the final material and shader work. Aided by photo­graphs projected directly onto the geometry in Maya and baked onto the UVs, the artists painted the face textures in Photoshop at a resolution of 2048x2048. The textures were used at full resolution in the pre-rendered cinematics, but downsized to 1024 pixels for in-game use.

While artists painted most of the textures in Photoshop, they used Infernal for skin shaders, including a subsurface scattering solution. “Since we have so many well-known celebrities in our game, we had to pay special attention to each one. A global solution just didn’t work,” says Gonzalez.

Staying in Character

Animating performances that captured the mannerisms and unique energy of each actor—from Peter Venkman’s (Bill Murray) deadpan face and slouchy strut, Aykroyd’s exuberance, and Ramis’s cool-headed seriousness, to Potts’ quirky Janine—was by far the game’s most crucial challenge. “When we first heard we were developing the Ghostbusters game, we went from total excitement to instant fear,” recalls Gonzalez. “We are making a video game that features five main [and recognizable] characters?”

Actually, there were more, all of whom have personalities that fans have grown to love. Because the developers were unable to motion-capture the actual celebrities, they instead found mocap actors who “did their homework in mimicking each character’s performance,” says Gonzalez. The best acting is not limited to the cinematics, however; the in-game animation system gives each ghostbuster access to character-specific animations. For example, when Peter isn’t in combat, he strolls around in his signature “slouchy Venkman strut.”

The game artists mimicked the trademark movements of the Ghostbusters actors, translating that into the animations, which are a combination of motion capture and hand animation in Maya.

Nailing that trademark walk and the unique body language of the other actors meant the team had to switch from Auto­desk’s 3ds Max to Maya right after the project was green lit. “We needed more flexibility when it came to making tools and rigs, and to taking advantage of Maya’s internal referencing system, which allowed several animators to work on the same rigs across different scenes even before those rigs were finalized,” says Gonzalez. This more flexible rigging solution, developed in Maya and called Genesis, features on-the-fly FK/IK switching. It also enables the artists to choose a rig that has a reverse foot setup for hand keyframing or a regular foot setup for mocap, and uses a single GUI for as many characters as are in the scene.

Facial animation would be the true test of success, however. The group spent a lot of pre-production time looking at films starring the main characters, and built a phoneme library in Maya that covered all the nuances of each character. Next, the crew exported those phoneme shapes into OC3 Entertainment’s FaceFX for auto-recognition capture from the voice track. Once integrated into Infernal, FaceFX was used to generate the huge volume of dialog lines in the game. Nevertheless, most performances were a combination of auto recognition and hand animation, or were completely hand keyed.

Though the game uses only two base heads, both are robust and flexible, with more than 40 bones. Because all the heads share the same mesh and Maya joint system, they were also able to share skin weights. Most heads are capable of more than 50 base shapes, which, in turn, can be combined into myriad shapes in FaceFX or Maya. The crew also wrote a MEL script to import the base auto-recognized lip sync into Maya, where artists could hand key a large amount of upper face movement into the eyes and brows, for example, on top of the FaceFX animation. “This allowed us to choose key moments to add more expressiveness to the characters,” adds Gonzalez.

While all the creatures and ghosts were hand keyed, Terminal Reality mocapped almost all the human-based animations using a Vicon motion-capture system, refining them in Maya before exporting them to Infernal. The title contains more than 2600 individual animations, including 40 blended animations on each ghostbuster, which facilitated transitions between normal and combat walks and runs, or even when driving the Ecto-1 vehicle.

The node-based blending system created specifically for this title enables animators and programmers to combine hundreds of raw animations using control variables and different blending techniques to create output states. The group also created a tool that would transfer all the mocap data from the joints onto the studio’s animation controllers, enabling the animators to add to the performance of the mocap while still using a rig they were familiar with.

Ghostly Weather

Signs of impending doom are everywhere in Ghostbusters, manifested in the surreal weather and lighting. Ominous clouds loom low overhead, casting an otherworldly light as they whip into a swirling vault at the opening of the portal to the beyond. Almost all the lighting effects were done inside Terminal Reality’s Infernal Engine.

“The creation of lightmaps and the radiosity pass can be set up to run like a renderfarm, so that one person’s machine is not tied up with the process,” says art director Adam Norton. “You can place and adjust lights in your scene, as you would do in most 3D packages, or you can use any emissive material in the game to cast light from an object, which will be calculated into the radiosity pass. If you place a model of a lightbulb in your set and that model uses an emissive material, the model will actually cast light. You don’t need to place any additional lights in the engine. This approach, combined with our radiosity, allows for the creation of some realistic lighting solutions.”

That said, Norton acknowledges that the group is making a video game—one based on a very popular Hollywood movie, at that. So a lot of the time the crew preferred to use Hollywood-style (three-point) cinematic lighting, rather than go for true realism. To that end, the artists placed lights to achieve maximum drama with colors, shadows, and so forth.

Times Square was the most difficult to light, with the seemingly endless maze of buildings reaching far into the gauzy haze, the dazzling neon signage mingling with flaring police lights, and the usually complex weather and sky effects. “Because it’s a large outdoor set, you can see much farther, meaning we have much more geometry visible throughout most of that set than we do in others. This meant we had to vertex-light a lot more geometry, which, in most cases, doesn’t look as nice,” says Norton. “The artists had to build the geometry with this in mind to make sure the lighting would be effective.”

The group still light-mapped the streets since the player is standing directly on top of them. Intelligently built geometry and the use of a robust radiosity solution—which generates the lightmaps and calculates them into vertex radiosity—helped make the set look as nice as the others, contends Norton. –Martin McEachern

Packing Protons

Each ghostbuster comprises just over 31,000 triangles, give or take 16,000 depending on the equipment the character is hauling. “The proton pack started as a one-to-one copy of the pictures provided by the Sony prop archives,” says senior effects and environmental artist Glenn Gamble. “After I modeled it in 3ds Max and brought it into the game, we slowly started changing it.”

Gamble built the complex backpack machinery and collaborated with the programmers to perfect the proton streams. As he points out, the stream in the movie is not accurate, so the game version needed to be “tamed,” since a gun that never hits the crosshairs can be incredibly frustrating for the player. The other major issue is that the beam in the movies had been hand drawn and animated, resulting in behaviors and thicknesses that were wildly different from scene to scene.

The proton pack was the game’s most expensive model, requiring extreme attention to detail and a raft of animations, not only because it is so close to the camera, but because it relays so much crucial information to the player. “The entire thing could easily have spiraled out of control and become incredibly expensive for the processor to handle, but we used a lot of tricks to mitigate its cost,” explains Gamble. “For example, I shared UVs with many of the fill areas on the pack, which allows for a much higher pixel resolution while using less texture space. To make it render faster, I took three days to remake all the ghostbusters’ equipment, including the proton pack, the upgrades, gun, trap, and miscellaneous belt attachments, so that it would fit on a single 1024x1024 texture.”

The pack itself comprises six separate models, with more than 40 individually animated parts, a full physics-driven custom hose simulation, and well over 100 custom particle effects.

The game's physics were handled within the Terminal Reality Infernal Engine.

In one of the more creative uses of Infernal technology, Gamble created a custom shader for faking the depth of the slime in the pack’s tubing. “In our original approach to the slime in the tube, we used a series of overlaying eight-bit transparencies, which is expensive and can create rendering issues. After doing some creative tinkering in the Materials tool, I found a better solution: Using a series of facing percentages (a node that returns a value based on a polygon’s angle to the camera), I was able to fake the thickness of the slime tubes with a fluid inside, while still maintaining a series of eight-bit alpha transitions with only one set of polygons.”

Indeed, the game is awash in effects animation for the proton packs and the spectacular incursions from the other side. “There are a lot of effects in the game…a lot,” says Gamble. To simulate the steam expelled from the back of the proton pack, artists used the Trifecta particle tools within Infernal. The steam is a high-speed, cylinder-shaped emitter with an even higher degree of drag. This forces the steam to shoot out fast but come to a quick stop, giving it a look of friction and dissipation.

“The stream is lit partially and dynamically by the surrounding light. I say ‘partially lit’ because even though the effect is illuminated by the surrounding lights, it never looked right,” says Gamble. “By blending between the light values of the set and a specified color value of the particle, I was able to re-create the right look.”

To create the bounce lighting emitted from the proton streams and reflected onto the characters, the artists placed a small dynamic light that is synchronized to the timing of the stream, or “wand,” and color coordinated. The light turns on and off as the player fires the weapon, lighting up the character and anything close to the end of the wand. Another dynamic light at the end of the beam gives the player the same bounce lighting effect when shooting.

Haunted Houses

The library was the first game level tackled by the team, which spent eight months perfecting the geometry and lighting, making it the benchmark for the rest of the game. Because the ghostbusters travel from the open air outside into the dimly lit halls of the library, the team spent a lot of time refining the lighting and radiosity system of the Infernal Engine so that the lighting transitions would be smooth and realistic, while the textured glass windows—mapped with an emissive material—could illuminate a room while the player could still see through them.

Once inside the library, cards erupt in a plume from drawers, walls catch fire, and books fly off the shelves. Incredibly, every book is an individual model that can be knocked off the shelf, kicked around, or shot at, sending it flying about the room via Infernal’s physics simulation. At last count, says Norton, there were more than 30,000 books in the library. “There are no tricks here; they are individual books. They’re persistent, too. If you want to spend the time shooting shelves, you can empty them all and push all the books into a giant pile,” he says. “I’ve done it myself a few times.”

The game’s most interesting villains—and the more unorthodox character animations you’ll find in the game—are the golems: shapeless entities whose form slowly coalesces as they draw books, coals, and anything else around them into their midst. “When we first discussed the idea of golems, we were going to use the traditional method of creating them from the 3D geometry and rigging them like a normal character,” says Norton. “But then, we all agreed to push the envelope a bit.”

The team devised a method of putting tags along the golems’ joints in Maya. The Infernal Engine would then make objects that surround the golem jump up and attach themselves to those tags. “The first test was a book golem. Everyone was excited to see how a character could form right before their eyes. We immediately started creating golems that had some interesting silhouettes,” says Norton. For the kitchen golem, who chases the ghostbusters through the Sedgwick Hotel, the artists assembled all his kitchen-related parts beforehand so they could choose the best silhouette for him. Once that was approved, they placed each part it in the kitchen, where it is usually found. When the character appears, each one of those parts levitates and attaches itself to the correct tag.

Infernal's dynamic cloth sim drove the garments worn by the Female Possessor

To make chandeliers and other luminescent objects glow realistically, the team mapped them with an emissive material in Infernal. For moving, incandescent entities, such as the coal golems, the artists first applied an emissive material in Infernal, and then added a dynamic light that moved around the set with the character, giving the effect that they are casting light onto nearby objects.

Artists developed the translucent appearance of Slimer, the fisherman, and the other ghostly entities with a mix of transparency maps and emissive materials created in Infernal. “The ghosts actually have very little diffuse [shading] applied to them. We wanted to control how much light they received from the environments, so we ended up isolating them from the environment altogether,” explains Norton. The artists ended up applying a custom lighting and particle solution to each ghost to help them resemble their movie predecessors. They also added volumetric lighting and particle effects to light fixtures and skylights in the museum, for example, to create atmospheric cones of light.

The character Slimer, with its squashed and stretched look, apears in the game. The model also has a customfacial rig with more than 10 Maya controllers in its mouth alone

When Venkman is bowled over and slimed in the Sedgwick, artists used lots of particles and materials, all created in Infernal, for the lime-green slime. “Basically, the alpha [channel] of the particle acts as a mask for the flowing ‘liquid’ underneath,” says Gamble. To create the liquid, the team used CrazyBump (available via the Web) to create animated normal maps of ooze running down his face and body.

High Spirits

Atari’s divine intervention last year proved timely for a couple of reasons. It delayed the game by seven months, giving Sony and the entire development team a long grace period in which to polish the game. And, coincidentally, it also aligned its release with the film’s 25th anniversary. “Typically, you start off a project thinking you’ll use the last three months to polish, but along the way, more features are added, massive changes or overruns occur, and that time is lost,” says Norton. “In this case, the art was all to a point where it could have shipped at the original release date. But when we got the extra time, Atari and Terminal Reality were smart in that we avoided adding new content. We just made what was there better.”

Now, only time will tell if Atari will be rewarded for its faith and if Terminal Reality will recapture and contain the spirit of the ghostbusters, and preserve it for a whole new generation…at least until the new movie arrives in 2012.

Martin McEachern is an award-winning writer and contributing editor for Computer Graphics World. He can be reached at