Chas Jarrett and his team at MPC created all the mayhem inside the ship. Their work concentrated on extending partial sets and creating full CG environments that included digital props, water, fire and characters.

Extending the Sets
Unlike the original movie, the overturning of the ship is spread out over a four-minute sequence encompassing dozens of exterior and interior shots. All the mayhem occurring inside the ship was created by MPC. The London-based team included visual effects supervisor Chas Jarrett, compositing supervisor Adrian De Wet, CG supervisor Steve Moncur and lead effects technical director Ciaran Devine. “We worked on over 200 shots, but about 80 of these were deleted from the final cut for editorial reasons,” Jarrett recounts. “Our work covered two types of shots: extending three partial sets of the inside of the ship, and creating full CG environments that included digital props, water, fire and characters.”

MPC first contributed set extensions to several scenes preceding the capsize sequence. The most complex set was the eight-story lobby. It was built on a soundstage as a two-story pie shaped set that covered 120° of the complete site. MPC completed the set by adding matching 3D geometries (derived from LIDAR data), and texturing them with photographs of the set elements. Built in Maya and lit with global illumination in mental ray, the CG stories were populated with motion captured CG characters. For the later shots of the grand staircase collapsing, MPC wrote a shattering algorithm to pre-break the mesh. Then, proprietary rigid body dynamics engine PAPI was used to constrain everything back together for the simulation. All the shots were composited in Shake.

For the capsize sequence, a gimbal rig was employed to rotate a small section of the ballroom set in front of a blue screen, which provided a live-action foreground. “We first extended the set with our CG ballroom environment and then, set out to populate it with literally thousands of CG elements,” Jarrett says. “We had 200 CG people, plus all the furniture that you can imagine: dishes, food, poker chips, playing cards, etc. It was incredibly complicated.”

MPC completed the eight-story lobby set by adding matching 3D geometries and texturing them with photographs of the set elements. The CG stories were built in Maya and lit with global illumination in mental ray.

To animate the CG passengers, MPC motion captured three categories of movements: people partying, people rolling and falling and, finally, injured people getting back on their feet or helping each other. Each category ended up with a library of about 300 different movements. “Some motions were used as approved pieces of animation, but most of the time, they were blended with other motions in ALICE, our crowd animation system,” Jarrett explains. “For example, we would capture somebody walking, and then, separately, somebody getting knocked over, and finally, somebody standing up again. The system allowed us to ‘throw’ an object at the walking character, at which point it would switch to the falling character, and then, to the character standing up, and finally go back to the walk cycle, all in one continuous move. Whenever the characters had to take a hard fall, on a chair for instance, or to roll around with other people, we used PAPI to create the dynamics of the animation. It was then blended with the motion captured motions.”

Switching to a mental ray Pipeline
Given the huge amount of moving objects in any given frame, the hero shots were designed in layers. First, the digital set was added in the live-action plate or created as a full 3D environment. Second, the biggest objects, like chairs and tables, were simulated, all rigged to break apart under a randomized level of force. Third, the people were added and the whole simulation was re-run again, so that the characters and the furniture would interact with each other. At that point, a multilayered cloth simulation was run in Syflex for each character. Fourth, the smallest objects, like forks, glasses or playing cards, were integrated into the scene and the simulation was re-run another time. Finally, one last simulation was run with confetti and balloons added in.

To create the collapse of the grand staircase, MPC wrote a shattering algorithm to pre-break the mesh and then used a proprietary rigid body dynamics engine to constrain everything back together for the simulation. All shots were composited in Shake.

The simulations ran in ALICE, with PAPI creating the rigid body dynamics animations, all within Maya. The images were then rendered, in many passes, in mental ray, which marked MPC’s first use of the software in a feature film. Adapting to this major switch in the pipeline added a lot of pressure to the team, but this effort was deemed necessary to exploit the full power of a new fluid simulation engine. “After looking into Real Flow and studying the option of writing our own application, we decided to license Flowline, a tool developed by Stephan Trojansky, head of R&D at Munich-based Scanline VFX,” Jarrett recalls. “What they showed us was far beyond anything that we had ever seen on the market. The basic concept of how Flowline does its simulation and the interface are very unique. I was especially impressed by its ability to generate CG fire that looked absolutely real. Most of all, Flowline was able to create water, oil, fire and smoke, and have them all interact with each other in one digital simulation without the need for any practical element. This was the ideal tool for Poseidon, as we had a scene in which oil drops on water and catches on fire, which produces smoke: all this was entirely created in Flowline. It can even generate dust: a function that we used for the collapsing staircase simulation.” The relationship with Scanline went beyond mere software licensing, as Trojansky became digital water and fire supervisor for MPC.

One particularity of Flowline is its need for a powerful ray tracer, such as mental ray’s, to function with all its features. The calculations in the rendering are mostly based on ray tracing and many of the surfaces are actually implicit surfaces, not real surfaces. “It required a real commitment from everyone in the CG department, as we had a lot of staff who were new to mental ray,” Jarrett concludes. “But I believe the results speak for themselves.”

One movie, two groundbreaking fluid simulation engines, both intercut with each other in the final cut… One thing is sure: on release date, the people at ILM and MPC will be the first in line to watch and analyze their peers’ competing water effects!

Alain Bielik is the founder and editor of renowned effects magazine S.F.X, published in France since 1991. He also contributes to various French publications and occasionally to Cinéfex.Last year, he organized a major special effects exhibition at the Musée International de la Miniature in Lyon, France.