Massive Mummy Clay Armies

Mummy 3 : Tomb of the Dragon Empero recently opened in secondary markets such as Australia. Digital Domain did some outstanding Massive work to bring the Armies of Mummy 3 to life, as well being responsible for the development and creation of the CG Emperor Mummy villain. We spoke to the DD team about their Massive experience and their procedural pipeline which is heavily reliant on Houdini.

Massive Army's by Digital Domain

Massive (Multiple Agent Simulation System in Virtual Environment) is a high-end computer animation and artificial intelligence software package used for generating crowd-related visual effects.

Massive was developed by Stephen Regelous, with version 3.5 announced recently at SIGGRAPH 2008 (LA). Its flagship feature is the ability to quickly and easily create thousands or tens of thousands of agents that all act as individuals. Through the use of fuzzy logic, the software enables every agent to respond individually to its surroundings. These reactions affect the agent’s behaviour, changing how they act and controlling motion-captured animations to create a realistic looking character. Reactions are based on a programmed Massive brain logic.

Nordin Rahhali, was the CG Supervisor on the Mummy 3 : Tomb of the Dragon Emperor which lies heavily on Massive agents to stage the various huge battle sequences in the film.

Massive was used extensively for the large scale fights at the end of the film. The agents were built on the back of motion capture sequences using Motion Builder. For each major setup the team would split the shot into layers of model detail, Massive agents were used in all the backgrounds and then as the characters got closer to camera they became a mix of Agents and hand animated warriors, until finally the very close to camera characters were fully hand placed. All the warriors were based on motion capture data provided by four weeks of capture by Giant Studios, well respected for their high end motion capture work.

Chad Finnerty was in charge of Massive animation for the thousands of warriors seen in the end battle. “The biggest thing was that the large scale battle was in bright sunlight…we had to get a certain level of detail in the agents animation that we have not really seen before.” In the final battle there are complex plot points involving multiple Agent armies coming together, for example side flanking hammer actions, with a total of four strategic pieces of choreography. As a result, Finnerty describes this film as one of the most complex Massive projects he’s worked on, with up to 10 artists working simultaneously.

According to Finnerty, a key decision was to have just one agent brain builder, James Thornton. “He was the main brain builder for the whole show, he would build the agents and maintain the agents for the whole show. The other artists would not alter the agents brains, they would actually issues request to him and then he would effectively release a new build of the ‘software’ or the agents, and this worked really well, as you did not have too many cooks in the kitchen!”

The other artists worked on five to ten shots, and each shot would take about three days each, mainly spent in the actual simulation time. On paper there were 1,800 Terra-cotta warriors and about 2,400 foundation warriors in the story, which is not huge, but the director selectively increased this number for dramatic effect, cheating the number much larger for epic effect to make sure formations broke edge of frame.

Massive numbers had to vary for dramatic effect

Typically, with a simulation of the complex humanoid agent types that Digital Domain was attempting, Massive recommends starting to break the scene into passes if the agent count exceeds about 10,000 to 20,000, so the number of agents were not the challenge in the Mummy 3, it was more the complexity of the movements and the number of shots required.

For Digital Domain, rendering was fairly standard RIBs (RenderMan Interface Bytestream format) and AMC data to the lighters. Massive can import or export motion in Acclaim motion capture (.amc) or Maya ascii (.ma) format. Massive can do software rendering through RenderMan renderers or high-quality hardware rendering directly from Massive. Mental Ray is currently not supported but should be available soon. DD used Renderman for Mummy 3, but found Massive to not be as open as say Houdini.

Finnerty was also very pleased by how close they could bring animated agents to camera. “There were several times where a massive character could fill half the frame,” he points out. Because the pipeline passed along the RIB and AMC files, if an animator needed to access the AMC data, they could import it into Maya and put the data on a standard rig and animate away, adding to or replacing whatever was needed. “Agents were also sometimes just pulled out of a shot if their character got a full hero animation” he adds, but the robust pipeline made this process very easy.

This pipeline approach is very evident in the way Houdini was used. The 3D package has always taken the procedural approach and it works very well with Renderman, explains Rahhali. “It is a very environmental package…and it has I would say the best RIB exporter of any package and that comes natively with it.”

RIB output from Massive could be imported into Houdini, where the shattering of coldiers from gun fire would be added, and then re-exported to the lighting team. Rahhali explains that the “lighting team would pick up the RIBs with all the same shader attributes that came through the pipeline…all the unique character attributes create that character. Since there was a good deal of procedural texturing per agent, there were only so many unique models we could paint or texturing”. Morten Larsen was the lead of the effects team and all of the Houdini workflow.

The army is seen either at rest or already in movement

While there was procedural cracking in the shading for shattering, there was no cracking that actually happened on screen when the army is fighting or marching. In fact, during the film, the viewer never sees the army starting to move. Via clever editing, the army is seen only either stationary or already moving. The moving warriors were rigged pre-cracked.

This is not the case with the Emperor. His character is “more magical” than the army and is fighting a constant battle of cracking and re-healing, where as this did not happen for the army itself. The crumbling and dust falling off the Army when it was in motion and the shader based cracks on their bodies were procedural. The texturing team was headed by Stan Seo.

To add realism to the Massive sequences, the team needed to have contact interaction from the agents to their environment. To achieve this, the team wrote a custom export from Massive that would show where all the footsteps would happen, so anytime the Agents took a step the team would know where they had been. These digital footprints were then imported into Houdini, and generate dust clouds, and even little foot marks on the ground where foot falls of small sand, based on the terrain, grass would leave less of an impression than a sandy terrain.

The quality of light really sells the shot

One of the aspects that the team worked very successfully on was the quality of light. “We had a great lighting pipeline,” comments Rahhali, and they “spent a lot of time trying to get the terra-cotta army right.” There were about a dozen real statues shot on location, so the team had very good visual reference. For every setup that would have CG statues, there was also a colour chart, a grey ball, a mirror ball and also a stand in terra-cotta solider for reference.

This was in addition to actual HDR 360 degree scans and captures. The mirror ball and grey ball, while not as accurate as the full HDR, is shot via the 35mm Cine camera and can be grabbed much more quickly. As such it is more likely to exactly match the final lighting setup than the full HDR scan done with the Canon 1DS, which sometimes needs to be done at odd times relative to the actual button on/button off of the shot as it takes considerable longer to do. In post the lighting team sets up a LookDev , when the CG lighters set up the textures and displacement maps on the models in a full HDR environment, with each model on a turntable.

In contrast to Digital Domain’s previous Speed Racer project, this project was heavily diffuse with almost no reflections; almost the exact opposite of the shiny Mach 6 and its fellow racers. But the weapons were designed to have glints and pings. So the terra-cotta army’s weapons had specific specular highlight solutions.

note the main spec highlights are found on the sword bottom right of frame

For both the diffuse soldiers and their pinging weapons, the real key to selling the CG were the atmospheric and dust effects that needed to be introduced. Digital Domain used Storm, its proprietary voxel renderer. “This pipes into Houdini…his whole show was very pipeline driven,” says Rahhali. “We just had to work that way, dealing with shots from a single hero CG character to thousands of soldiers filmed in a wide/macro view. We are dealing with a variety of packages too. We have Maya for animation and lighting , which pipes into Renderman. We had Houdini for all the effects, all the volumetrics, all the shattering, and all the hero cracking on the Emperor Terra-cotta. And we were using massive to build all the armies,” explains Rahhali.

In terms of props, The Foundation army carried a range of farm tools, such as a pick axe, and while the Terra-cotta army had a smaller set of possible weapons, but with varying spear heads or crossbows and other procedural rotation variations from the massive brain.

Digital Domain did some 300 shots, working right up until the last minute to deliver the film. One shot that came late in the production saw the entire army shattering. This had not been originally in the script. The team turned to Massive and used the Massive Dynamics to shatter the entire army and that ended up being one of the last shots the team worked on and close to the last they had approved and turned over.

The renders from 3D to Nuke were passed as a multipass OpenEXR, allowing the compositors a great deal of freedom in ‘selling’ the shot and adjusting it in the comp. The team produced the renders using a fully ray traced approach with ambient occlusion in Renderman.

Jet Li crumbles

Jet Li and his under mummy effect complete with composited live action fire comped in Nuke

Jet Li’s character has an effect the team called the ‘under mummy’. In the film, his character is cursed and this would result in him oozing liquid terra-cotta, until he gets fired up by a magical fire that forms into a digital ceramic Jet Li, with digital burn skin and dececated remains under the terra-cotta skin. To make our hero’s lives more difficulty the character could also breath aggressive fire.

As Jet Li’s Emperor is covered with either cracked terra-cotta or burnt skin, a key aspect was his eyes. The eyes really needed to carry the performance and the eyes which audiences see in the film – while based on the actor’s eyes – are fully digital. This added a real weight on the animators task, to both study the real actor’s performance and to gain a full range of expression for the whole performance just from the eyes. Since so much of the rest of the digital character was either burn or stiff ceramic, a shot could hinge on the quality of the eye animation.

The eyes needed to carry the emotional acting range of the performance

Another challenge for that the environment plates filmed in China varied from normal to extremely foggy/smoggy shots with very poor visibility, yet the film takes place in the 1940’s before the industrialization of China, in a time when air quality was presumably much better than it is today. So many of the plates or horizons/skies of the background plates needed digital matte painting or full CG environment replacements.

Digital Domain continues to push the boundaries of complete digital environments combined with large scale crowd/people simulations.


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