Twists and Turns: Inside the ird Floors Previs and Postvis for the Maze Runner

Twentieth Century Fox's motion picture The Maze Runner (based on James Dashner's book) finds a group of teens facing a labyrinth of giant proportions. Between massive walls that reconfigure and deadly enemies on patrol, solving the maze - and finding an exit to their reality - presents challenges at every turn.

In the movie, the characters strategize to carefully map out their environment. In making the movie, Director Wes Ball did the same, using previs to help plan flow of action, character and camera movements, set construction, and CG effects.

One of the goals with the previs was helping work out camera angles and movements within the maze, said Jourdan Biziou, previs supervisor with The Third Floor Los Angeles. We were able to configure the maze in various ways to visualize the action and timing the director wanted. We also set up virtual cameras so the filmmakers could view potential coverage and make choices about on-set and visual effects requirements, such as which walls needed to be digital or practical.

(For an extensive look at the visual effects, see Amazing in the September/October 2014 issue of Computer Graphics World.)

Previs assets - human characters, creatures, environments - were modeled and animated into previs scenes using Autodesk Maya, with comps of additional layers and simulated effects in Adobe After Effects. The team based their work on a variety of concept artwork as well as a video mockup the director had created himself.

Wes, who has a very strong background in visual effects, created a video in [The Foundry's] Modo as a guide for us in creating the previs assets, Biziou recalls. In the video, he literally walks through a mockup of the maze, talking about motivation of the characters, doing his own animations of particular actions, and characterizing different maze sections - the vast open glade at the center, the shadow-filled narrows along the walls, and a forest of metal fan blades in the outer reaches. It was fantastic to have a director understand and communicate his ideas so well.

One of the first sequences The Third Floor previsualized was a scene where two boys - Thomas and Minho - run into the maze to help another character. Working Visual Effects Supervisor Eric Brevig, Biziou, and Motoki Nishii, head of The Third Floor's asset department, plotted out sections of the maze using a fixed number of physical set pieces that were going to be built on stage. They numbered those pieces and combined them into various setups that could be switched whenever the boys rounded a corner and entered another area.

Bluescreen was dropped in at points where digital set extensions were anticipated, and the previs team also calculated camera speeds and distances based on the DPs' selected rigs.

Another important sequence demonstrates the scope and power of the maze as it rearranges. Wes wanted to show the variation of transforming from one place to the next, from the fan blades to crazy, giant blocks shifting and transforming, all based on the architecture of the maze as a whole. He had a good idea of where he wanted the characters to go within the scene, and it was a great collaboration in the previs sandbox' to develop specific ideas for the progression that kept up the intensity - are the boys going to make it, and what is coming at them next?

Other key sequences involved reveals and chase action with the Griever creatures. The Third Floor created Griever previs models using concept art together with evolving designs from production and visual effects. In the previs scenes, artists focused mostly on gross movement and placement of the Grievers in relation to the space in the walls and the humans.

In postproduction, The Third Floor's artists replaced bluescreens with previs backdrops and accurately animated previs Grievers into plate photography to provide working postvis versions for the filmmakers, editorial, and visual effects. In postvis, they animated the previs Grievers and their nasty and scary movements more precisely, Biziou says. The production had filmed guys in blue pajamas running around playing the creatures so the actors could move and react naturally to what ultimately would be CG characters. So we had a lot of visual cues in the postvis phase.

One scene - the fight in the Griever Hall - featured a significant amount of creature animation together with fast, hand-held camera moves, an especially tricky combination for postvis. The Third Floor tracked the plates in [Vicon's] Boujou, then hand-keyed them to ensure smooth tracks that matched up to the digital set.

This sequence had about 13 kids with spears fighting off Grievers. The footage was fast moving and hand-held so tracking markers used on set would vanish in a blur, says Biziou. After carefully tracking the shots, artists used After Effects to composite the previs Griever Hall environment, created in Maya, into the live plates, replacing the bluescreen. From there, previs Grievers were animated into position to complete working temp versions of the scene.

We interfaced with Wes and Eric throughout our process, and during postvis we got to see some of the wonderful animation and final visual effects Method Studios was creating for the sequences. The show was a great collaboration and it's amazing to see the final results on screen, Biziou added.

All images copyright Twentieth Century Fox; courtesy of The Third Floor, Inc.

LINK:	http://www.cgw.com/Press-Center/In-Focus/2014/Twists-and-Turns-Inside-...
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