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Issue: Volume 36 Issue 6: (Sept/Oct 2013)

Iron Man 3 Previs

By: Martin McEachern

The Third Floor designed several action sequences for Iron Man 3, among them, the military chopper attack on Tony Stark’s seaside estate, the suit connect test, the crash landing in the forest, the freefall air rescue, and the battle at the oil tanker.

For re-creating the Malibu mansion carved into the seaside bluff, the artists worked from the technical specs of the living room and garage sets built on two soundstages in North Carolina. Working in Autodesk Maya, they built scale versions of the living room, the garage, and the façade of the house, all of which were destroyed by the choppers.

While maintaining the spirit of the animatics, the team also had a particular request from Marvel: The comic-book giant wanted the previs to match the painterly look of the storyboards, so it could be seamlessly cut into the edit.To that end, the team left all its previs assets gray-shaded, occasionally overlaying them with painterly textures.

"This look continued throughout all the sequences, allowing us to concentrate on story points and not get tied down with the color or material of objects, lighting, or performance," says Previs Supervisor Todd Constantine. As the work progressed, the team replaced shots in the animatic with the detailed previs, showing, for example, whether the set would accommodate the shots, if a lens would work, where actors needed to stand when explosions went off or floors collapsed, and so forth. The team also provided techvis for numerous scenes, calculating camera heights, shutter speeds and lenses, and helping the crew quickly implement the data as scenes were being shot.

For every sequence, artists modeled and hand-keyed their assets in Maya, including character animation, effects, and camera work. They did, however, utilize the company's motion-capture suits to record performances for the Suit Connect scene. Aside from Maya, The Third Floor also uses Autodesk's MotionBuilder for animation and Adobe's After Effects for compositing. Most of the geometry is kept light to ensure that scenes Playblast rapidly in Maya.

"Turnaround times are very important, especially when getting closing to the start of filming," says Constantine. "Since our scenes aren't rendered, we don't use complex techniques, but we do bake in ambient occlusion on assets when needed. For our previs and postvis shots, we rely solely on OpenGL hardware renders, allowing artists to render shots in a fraction of the time than it would take via other renders." With this method, says Constantine, the crew could render most shots in 10 minutes or less.

As the attack choppers rake the mountainside mansion, artists simulated the destruction using a variety of simple particle effects, including emitters for missile trails and smoke from fires. They also used emitters for the snow in the Forest Crash sequence. "Anything that can be played back through the Viewport and Playblasted quickly in Maya is something we try to work with. Occasionally, we do run destruction simulations on a large set piece and use it as a compositing element. But this usually takes too long, and most times we can hand-key destruction mixed with simple effects more efficiently."

Close collaboration with all the departments was vital, given the level of action in the film, says Constantine. "While the director always has final say, their ability to brainstorm with the previs department varies. [Director Shane Black] was busy writing the script, so his time was split between many different responsibilities. We mostly interfaced with Chris Townsend, the VFX supervisor, incorporating his ideas before showing Shane. Shane would then give us his notes, which we'd address for the next time he came in. During the Seaport Battle previs, we had the Second Unit director sit in with us for several weeks, because he was shooting most of that sequence."

In addition, Cinematographer John Toll would study the previs intently, suggesting things that needed more refinement or would be better left resolved on the day of shoot. After several rounds of revisions with Townsend and Black, artists completed the sequences in an edit that covered key technical and story points, could be shown to cast and crew as a plan of attack, and captured a full movie experience, replete with a temporary soundtrack and sound effects.

Postvis Power

The postvis team, led by Postvis Supervisor Gerardo Ramirez, set up shop on the North Carolina set just down the hall from the editorial department, quickly compositing shots so Black could evaluate footage and figure out if he needed another angle or performance.

 "I'd discuss the animation and visual effects of the shot with Chris to ensure that the postvis version fit the style of the film," says Ramirez. "We touched various scenes in the film, including the Malibu Mansion Attack, the Crash Landing in the Forest, and the Seaport Battle. For the Mansion Attack, because the scene was so heavily previs'd, the postvis team was able to composite several animations and effects from the previs right back into the live-action footage."

For shots that required compositing CG elements into a plate with a camera move, artists would use Vicon's Boujou to matchmove the camera. After importing the tracked camera into the Maya scene, they would animate the effects, set extensions, and actions. "We did this for shots involving Iron Man's suit fighting off Extremis Soldier atop cranes in the Seaport Battle, or suit pieces attaching to Tony's body in the Mandarin Mansion Escape sequence," says Ramirez.

 "For most of our postvis, we created custom animations or used motion capture for the actions. However, for several shots we were able to reuse animation and effects created for the previs version of the shot." For shots that needed mocap, the crew used an Xsens motion-capture system running MVN Studio software. "Using MVN Studio, we could clean up the mocap data and export it as an FBX file, which, in turn, could be applied to our digital characters within Maya."

When shots didn't require a 3D camera move, the postvis team would composite elements onto the plates using After Effects. Because artists did all the 2D compositing using After Effects, the company developed custom tools to streamline the workflow between Maya and After Effects.

"For example," says Ramirez, "when artists were done animating in Maya, they would click on a tool that rendered out their elements and loaded them into an After Effects template. The template organizes the elements and inputs all the technical data into the slate. This allowed them to focus their efforts on creative aspects while leaving the technical tasks to the scripted tool." The postvis team also drew upon a large library of stock footage of explosions, sparks, smoke, dust, and animated graphics to rapidly forge a sense of realism.

After matching Marvel's painterly style in the previs, the artists were allowed to explore a greater level of realism in postvis. "We created new textures for our assets so they would blend in with the plates that were shot. We try to keep it as cinematic as possible, letting the sequence speak for itself as a piece of entertaining storytelling," says Constantine. "Our shots aren't rendered: They come straight out of Maya's Playblast capabilities, which lets us turn around the work in the shortest amount of time possible for the client. To give it that special level of detail, we incorporate effects, shading, lighting, and so forth directly into Maya, with some simple compositing tweaks and 2D effects added in After Effects."

While the previs phase will draw input from many departments, postvis, on the other hand, is driven mostly by the editorial team, says Ramirez. "Shane would give his notes to the editors, who would then adjust the edit and pass any related notes to our postvis team."

A Vision Realized

Once the previs and postvis was complete, The Third Floor provided the information to the main effects vendors on the film. "I'm proud to say that most of the shots we developed for the scene are in the final movie," says Constantine.

As Constantine notes, the previs process helps bring the director's vision to life on the screen. "I've worked with directors who like to direct right over your shoulder. Early in the production, they might have time to discover the possibilities of shots in sets that have yet to be built. This is rewarding because you get to witness firsthand the director's creative process," he says. "Other times, we'll get fully boarded sequences and a directive to follow them exactly. The artist will animate to the compositions, concentrating on pacing and kinetic energy. Sometimes, the boards don't work in motion, and we have to tweak the overall intent."

 

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