To Hell
Issue: Volume: 33 Issue: 5 (May 2010)

To Hell

Artists at Visceral Games take players to the depths of the netherworld in Dante’s InfernoIn the 14th century, Dante Alighieri set the world ablaze with his allegorical tale “The Divine Comedy,” an imaginative epic poem that describes his journey, as the main character, through the three realms of the dead: Hell, Purgatory, and Paradise. The piece is considered one of the greatest examples of world literature, serving as an inspiration for many artists throughout the past several centuries, from Geoffrey Chaucer and John Milton, to Henry Wadsworth Longfellow, Karl Marx, and T.S. Eliot. And more recently, the 3D artists at Visceral Games, which used “The Divine Comedy” as the basis for its Dante’s Inferno computer game.

“Dante’s Inferno is a big, epic action/adventure game that’s loosely based upon Part One of ‘The Divine Comedy,’ ” says Jonathan Knight, executive producer/creative director of the title. In fact, it is Knight who is credited for the game’s conception.

The original literary work presented a spiritual journey in which Dante, halfway through his life, becomes assailed by three wild beasts after becoming lost in a dark forest. He is led from the woods by the Roman poet Virgil, first to Hell and then Purgatory, where Dante must overcome obstacles—temptation and sin—to achieve the ultimate goal: eternal bliss in heaven, guided there by the “ideal woman” Beatrice. The interactive title, from Visceral and published by EA, places a contemporary spin on the poem. In the new medium, Dante, a mercenary soldier during the Third Crusade, pursues dark forces that have dragged his beloved Beatrice to the fiery depths. During this journey through the afterlife, the player, as Dante, must battle hideous monsters within the Nine Circles of Hell in an attempt to save Beatrice. The game—which plays out within the first cantiche, or part, of the three-part poem—ends as Dante leaves Inferno, or Hell, and makes his way to Purgatory.

Hellish Vision
While “The Divine Comedy” offers a haunting description of Hell’s nine circles, Dante’s Inferno goes one step further, giving it a visual interpretation under the art direction of Ash Huang. “The game brings to life the vivid and detailed worlds imagined by Dante Alighieri,” says Knight. “Each of the Nine Circles is its own world, with unique art direction, environments, effects, creatures, and back stories.” Huang worked with lead concept artist Jeff Adams, and together they forged Visceral’s contemporary vision of Hell. Huang and Adams worked on the game’s concept art throughout production, from the initial stages all the way through content lock. “Given the original nature of so many of the creatures and environments, concept art was an integral part of every step in the production,” says Knight. In fact, concept art was made for every facet of the game: characters, environments, props, weapons, the UI, and cinematics. Further direction was provided through 2D and 3D storyboards.

The detail in the game’s imagery is apparent here, in Hell’s City of Dis, as Dante makes his way to the Circle of Anger, to face the molten giant Phlegyas.

Hell’s Inhabitants
The characters of Dante’s Inferno range from the realistic knight Dante and the beautiful Beatrice, to the hideous Lucifer, and all manner of monster and creature in between. The character model concepts were driven by the sins by which the characters were condemned in Hell: Limbo, Lust, Gluttony, Greed, Anger, Heresy, Violence, Fraud, and Treachery, the Nine Circles of Hell. The theme from each sin is incorporated into the character design—Gluttony’s multi-headed, mouth-snapping Cerberus is but one example. The concept designs for these characters were created in high detail using Pixologic’s ZBrush, and then optimized in Autodesk’s Maya to adhere to in-game polygon budgets—a process Erik Holden, technical art director, says proved particularly challenging throughout the game’s production.

Once the concepts were approved, the team—guided by lead character artist Vince Fung and senior character artist Lisette Titre—began building models, starting with a low-resolution in-game version first, before tackling the high-res sculpt in ZBrush. Then the artists moved to coloring and incorporated fine detail in the models, until they reached the desired visual quality. At that point, the ZBrush assets were optimized and re-exported back into Maya, before they were integrated into the Visceral Games proprietary engine. The characters—from the gigantic Cerberus to the knee-high unbaptized babies—are visually complex, with their costumes sometimes consisting of visual effects elements. As a result, the character modelers often worked closely with VFX leads Jeff Kuipers and Sandy Lin, as well as VFX artist Seth Hall, on combining the model and effects assets to complete a character’s look. Holden points to the smoke Lucifer and fire minions as prime examples of this workflow.

Some of the so-called “bosses” in the game, such as Cerberus, Phlegyas, King Minos, and Cleopatra, required more attention than others. “In several instances, we had to rework the UV layouts to give more resolution to specific parts of the character that got unexpectedly close to the camera,” says Holden. “Changes in gameplay cameras gave us fits from time to time.” Without hesitation, Holden names Gluttony’s Cerberus, with its three unique heads, long necks, and large-body appendages, as the most difficult character to create: Each head and several of the satellite heads had functioning mouths, complete with wagging tongues and gnashing teeth. Characters whose surface style varied greatly were particularly hard to texture—some characters had flesh, cloth, metal, and fluid in the same surface area. Using a combination of Adobe’s Photoshop and ZBrush, the crew created the various texture maps: diffuse, color, normal, specular, reflection, ambient occlusion, and chrome. Due to time and resource constraints, the artists used photographic reference or painted textures for the diffuse maps, and then derived normal and specular maps with Photoshop or Ryan Clark’s CrazyBump for non-specific surfaces.

“For some of the more organic surfaces, such as many of the intestinal-shaped floors and walls in Gluttony, we used ZBrush to create all the maps,” says Holden. “These worked well and, as intended, were quite grotesque.” For some objects and more specific environmental elements, like the tormented human figure statues, the group did a full ZBrush sculpt, exporting low-res geometry and a full set of textures.

Just as there was a range of character models used in the game, there was a similar range of animations required for them. The animation and rigging primarily was done in Maya, where it was hand keyed. Aside from the usual biped variety, there were characters that required special rigs to account for tentacles, wings, and other appendages (some quite unusual and others quite imaginative). “Let’s just say we weren’t limited as to how far we could push our characters,” says Tristan Sacramento, lead character animator. As Sacramento points out, the in-game animations were the result of a collaborative effort among the animators, designers, and programmers, who worked in little pods, enabling them to get things done quicker and more efficiently than if they had kept the departments separate. “Many ideas came from random conversations while getting coffee or just by standing in a person’s cubicle,” he notes. After an idea was initiated, “we quickly prototyped and tested it in-game to see if it is actually any fun. If we saw the potential, then we would go through the motions of getting an animation from blocking, all the way through to final. Being able to quickly iterate and see the animations in-game is key. An animation is not final until all the little bells and whistles—blends, rumbles, shakes, and VFX treatments—are added.”

While working in those pods, each animator was able to explore his or her own preferences for a particular character. Sacramento, for instance, started by looking at reference from games, movies, YouTube, or even film clips he took of himself performing various movements. “Acting out your animation gives you a better sense of how the animation should feel and where the weight and force is coming from,” he adds.

The most difficult animations were the full-on cinematic QuickTime events (QTE), which consist of the player character, an enemy character or two, some weapons, a few cameras, and likely a piece of the environment. “These animations tend to be on the lengthy side,” Sacramento points out. “Considering that an average attack animation is roughly 45 frames for a single character, these QTEs can range from 500 to 1000 frames for all the components.” Moreover, these sequences usually include two to four branch points where the player can succeed or fail, and the failures have to be animated separately for each branch.

“Managing all these parts of the sequence can be daunting,” Sacramento adds. “Yet, these are most likely the highly memorable moments in the game.”

A character’s aesthetic reflects the sin associated with a particular Circle of Hell wherein the character can be found, including Anger (top) and Gluttony (bottom).

Nine Circles
The environments, like the characters that inhabit them, have a unique theme and are reflective of the sin associated with that particular Circle of Hell; these are in addition to three smaller levels used in the lead-in to the game. In Lust, the architecture contains sexually suggestive forms; in Gluttony, the landscape resembles the internal organs of a creature. As a result of their specificity, very few of the environments could be reused, creating a tremendous amount of work for the environmental artists.

Because Inferno runs at 60 frames per second (nearly double the average), there was not much wiggle room when building the environs, particularly when there was more combat than usual (which created the added expense of the associated effects). According to Holden, there were times when the budgets ran over, requiring the group to strip down the environments to free up clock cycles for extra characters or combat elements.

“Strangely, one of the smallest levels caused the biggest headaches,” says Holden. The Phlegyas Rampage level, wherein the player controls the giant demon, gave the group “fits” with the frame rate and caused a lot of rework. “The level was simple enough,” he notes, “but the fact that Phlegyas walked through the environment destroying buildings with a breath weapon and his fists generated a huge number of particles, which ate up frame time like crazy. We had to use the simplest environmental shaders to get it to work and be as exciting as we had envisioned.”

To facilitate the environment creation process, the team, led by Rich Larm, devised a system to render textures in-game at 60 fps with the studio’s particle system. They were created in an off-screen buffer and then used with any material for environments as well as characters, visual effects, and so forth. “You can get an animated but infinitely variable texture and normal map this way,” says Holden. “We did the writhing bodies in the wall-climb, fluids, and more with this system.”

In Kuiper’s opinion, the area within the circle of Anger presented the effects team with some of the biggest issues. The environment is wind-torn, the sky boiling, and lava and steam boil from below, while at the same time, Phlegyas smashes the arena and blasts Dante with fire attacks—while other enemies descend at the same time. “During all that, Dante can do any number of VFX-intensive magical attacks,” he says. “Balancing high-quality VFX with performance was more difficult on this game than any other I’ve worked on.”

Inferno had two lighting leads: Matt Christmann, who focused on technical issues, such as tool scripting and support, feature requests, and testing; and Rachel Cross, who focused on artistic and production issues, such as artist collaboration and mentoring, tracking, and communication. However, as art director, Huang set the color script for the title and reviewed the lighting progress throughout to ensure consistency across all the levels since different lighters often handled adjacent rooms. Associate art director Meagan Carabetta provided lighting concepts for each zone, painting over unlit screenshots to provide a snapshot of the final look of the game. This gave production a clear picture of what the end result should look like so that no time was wasted on unwanted work.

The team used a number of lighting techniques, including occlusion, which was baked in using Maya’s Mental Ray (from Mental Images). In addition, the crew used direct and indirect illumination using Illuminate Labs’ Turtle, baking most of the environmental geometry light into the vertex colors. At runtime, dynamic lights were used, and according to Christmann, each mesh could be affected by as many as eight light sources, depending on the shader—vertex-shaded point lights, pixel-shaded point lights, and directional lights, for instance.

Visceral Games thought it necessary to judge the quality of the geometry in-game, says Christmann, so lighters had two dual-CPU or quad-core Xeon workstations with 4gb of RAM, allowing them to set up and iterate on two scenes simultaneously—polishing the one scene while the other baked.

Despite these steps, the game’s 60-fps render cycle remained an obstacle. Lighters were careful as to where they spent their cycles; lighters and environmental artists made trade-offs so that they could adhere to the budget. In many cases, the crew was able to use low-res shaders in the backgrounds, says Christmann.

The game, for the most part, is forward-lit, with Dane’s cross being the only per-pixel point light. “It’s always stuck on the hero, so the player will always be moving per-pixel detail around the gameplay, says Christmann. “For the in-game characters, this light was stolen to improve lighting quality.”

The directional shadow-casting light affected the character and environmental shaders differently. This lighting method was used for depth-map shadow, while character shaders also received diffuse and specular illumination from this source. Meanwhile, environmental shaders received only specular illumination, as their diffuse lighting was already pre-rendered in Turtle. This added some per-pixel illumination detail without washing out or over-brightening the scene. Specular cube maps also provided another source of per-pixel detail.

Meanwhile, many of the things that people assumed were lighting elements—light beams, glows, fire, and so forth—were done by the VFX artists during their passes through the world, Christmann notes, and not by illumination methods.

An Effect on the Game
Inferno is packed with visual effects from the beginning to the end. The title has many traditional environmental effects: water, fire, wind, fog, lighting, and weather. In addition, Hell has many specific effects, such as boiling skies, the dead plunging on fire from the heavens, a tornado of tormented souls, or sinners boiling in rivers of blood or lava. “For the first time, we had characters made completely of fire and smoke that were made entirely of effects,” says Kuipers.

Other notable character effects include Phlegyas, a 50-foot-high molten giant who breathes fire and goes on a rampage demolishing buildings in Hell’s city of Dis in the Anger circle. In addition, Dante has dozens of VFX-intensive magical attacks, and each boss battle with Minos, Cerberus, and Lucifer was packed with its own unique effects. VFX were even used to do final color tuning from level to level and other postproduction touches, like bloom, depth of field, and motion blur.

Visual effects, most of which were created with Alchemy, Visceral’s proprietary VFX system, are commonplace within the environments, adding to their overall complexity.

To generate the effects, the team used Alchemy, the studio’s proprietary VFX system, as well as an in-house materials and shader system, Maya, and Photoshop. Alchemy, though, did the heavy lifting, accounting for 95 percent of the work, while the in-house materials system enabled the artists to create custom shaders for specific uses, such as water or tornados. Maya, meanwhile, helped build mesh particles, do fluid and dynamic simulations, and generate textures for animated fire, smoke, and blood, for instance. Photoshop enabled the artists to hand-paint various particle textures.

Kuipers describes Visceral’s particle system as “feature-rich,” allowing for a great deal of flexibility. “We have a concept of ‘smart’ versus ‘dumb’ particles,” he explains. “Dumb particles are extremely cheap, and we can put thousands of them on screen at the same time because they use pre-calculated data. Smart particles can be interacted with dynamically, using forces, wind, normal mapping, or collision. They are more expensive, but when we need that extra control or interactivity, they are invaluable.” The team also used meta particles, mesh particles, stretched particles, and distortion particles to achieve the desired outcomes.

As Kuipers explains, Alchemy is so much more than a particle system; it is a sophisticated VFX sequencer. “The particle system is just one small part of what Alchemy is,” says Kuipers. He explains: “Think of it as a real-time compositing package, wherein each VFX is made up of multiple layers, and each layer can be a variety of different types, called ‘modules.’ Some of the modules the VFX artists have at their disposal include particles, procedural geometry, trails, distortion, dynamic lights, optical effects, light beams, decals, motion, forces, shape emitters, post FX, masking, messaging, and even sound.”

Lest we forget, this is Hell, so fire was an absolute necessity. To create that effect digitally, the group used a combination of various elements, including procedural geometry, particles, animated textures, and dynamic lights. Maya Fluid Effects provided specific looks for the animated fire texture sequences. “We had to make the fire look believable and perform well at 60 fps,” says Kuipers. “Normally, we layer many elements to keep the fire looking as random as possible. However, with our performance constraints, we had to be careful with overlapping elements because the fill rate was our big performance killer.”

Another challenging effect involved the Smoke Lucifer, which had to be a reasonable in-game match to the prerendered treatment given the character in the cut-scenes. The prerendered version consists of fluid-dynamics-driven smoke and millions of particles. The in-game version, meanwhile, had to approximate that look in real time and maintain the frame rate. “This was no small task to pull off. Maintaining 60 fps was our biggest challenge across the game, especially when there were a lot of effects on screen combined with lots of combat,” Kuipers points out.

By confronting potential digital imagery demons from the beginning, the artists at Visceral Games were able to avoid falling into a hellish nightmare during the title’s two-year development period. This allowed the team to accomplish its goal of sending players to Hell, a visit—in this instance—they welcomed. But at the end of their journey through the Nine Circles of Hell, players receive a divine reward: Purgatory, which is also the next cantiche (main part) in “The Divine Comedy,” thus opening the gate wide for a sequel to the game.