As Aslan would probably say, communication is key. All images © Disney Enterprises Inc. and Walden Media Llc. All rights reserved.

The practice of digital asset sharing will become more common as film effects become increasingly complex, deadlines tighten and studios look to multiple vfx houses to get their projects done on time. Three companies—Rhythm & Hues, Sony Pictures Imageworks and Industrial Light & Magic—recently came together to complete more than 1,400 vfx shots in The Chronicles of Narnia: The Lion, The Witch and The Wardrobe. Here are some of their guidelines for sharing assets and shots.

Communicate Early and Often
Executives from all three companies stress the need for early and direct communication among all the vfx houses working on a film. This back-and-forth should occur as soon as a production knows it will be using multiple companies for the work, even if the details aren’t yet ironed out.

On Narnia, Rhythm & Hues originally won the job, but Imageworks and then ILM were brought on board because of the sheer scope of the project. In the early going, however, it was unclear which house would do what or which shots would be shared. “It was a ‘what if’ proposition at the beginning,” says Scott Farrar, vfx supervisor at ILM.

Because of the initial uncertainty and the proprietary issues involved, the three houses communicated at first only through intermediaries from the production. “We had a non-technical person as the go-between on all these technical issues,” reports ILM’s Lindy De Quattro, who served as associate vfx supervisor on Narnia.

The early lack of direct conversation led to a number of complications. For example, one house might receive a file from another house that was lower-res than necessary, was created in an older software package or contained a less-than-optimal amount of data. This situation occurred not because of proprietary issues or technical differences, but simply because the two studios weren’t talking directly about what formats and information would be best given the assets’ end use.

In some cases, a house ended up having to rebuild models, especially for background characters. “You want to avoid having several companies build the same leopard,” says John Clinton, vfx producer at Sony Pictures Imageworks. While dealing with variables is a fact of life in the VFX business, he adds, the variability is compounded when there are several houses working together, and upfront planning is essential to minimize it. “You can have more consistency, which will breed efficiency.”

Eventually, all three houses met, along with vfx supervisor, Dean Wright, at Frozen Lake, the production hub for Narnia. “There’s nothing like meeting face-to-face when you want to get something done,” Farrar says.

Rhythm & Hues’ vfx supervisor Bill Westenhofer had to share assets with Sony Imageworks’ John Clinton and ILM’s Lindy De Quattro and Scott Farrar like no other project previously.

Scheduling is Key
One of the things ironed out at Frozen Lake was the schedule. “Scheduling was probably one of the biggest issues for all of us,” adds Clinton. “We all have our own internal schedules and internal conflicts. And the conflicts get exponentially more complex when there are three houses involved.”

For shared shots, one issue to be resolved was the order in which houses would complete their work. In general, the house doing the background layer had a given shot first, animating and compositing its work into the plate before sending it to the house doing the middle ground. That house would then comp in their characters and send the shot to the company doing the mid-foreground, which in turn sent it to the house working on the extreme foreground.

The executives at Frozen Lake also had to work out who would take care of the final composite and film out on each shot. It was decided that whoever was scheduled to have the shot last was responsible. In practice, however, both the order of completion and the responsibility for final comp and film out sometimes changed as color problems or other issues came up along the way.