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Chronicles of Collaboration

Karen Raugust reports on the importance of how three vfx houses developed guidelines for unique digital asset sharing while collaborating on The Chronicles of Narnia.

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 companiesRhythm & Hues, Sony Pictures Imageworks and Industrial Light & Magicrecently 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 arent 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 ILMs 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 werent 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. Theres 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 ILMs 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.

Finally, the three houses worked out due dates for each step in the process. Shared shots were scheduled first, since they would take the longestsome featured almost every character in the movieand had the most potential for glitches and delays.

The master schedule caused individual houses to keep shots active while waiting for later characters to be added, rather than having them signed off and moving on, as would be the norm. All studios have reels they want to close at a certain time, Clinton says.

Rhythm & Hues vfx supervisor Bill Westenhofer reports that there were a few instances in which his company would comp a character into the background with a matte and get the sign-off, rather than waiting for all layers to be completed. This step was taken not for technical or creative reasons, but simply to free up disk space.

Any delays within the intricate schedule affected all the subsequent due dates for a given shot, with the burden being the greatest for the house receiving it last. De Quattro recommends that studios build in some sort of allowanceeither monetary or timefor the company doing the final comp. It faces the most pressure when houses who have the shot beforehand miss deadlines, and it often has to assign more people to that shot to make the final due date.

In addition to shots where each houses work occurred within its own layer, there were some more complex situations where characters animated by different houses came into direct contact with each other. For example, there were scenes in which Rhythm & Hues lion, Aslan, touched one of Imageworks wolves. In this case, one house was typically assigned as the lead on the shot, with the animation data, fur mattes and other information sent back and forth between the two houses as the scene was finessed. The blocking period during animation was longer than usual, Clinton offers.

Only general geometries can be shared because other 3D information such as textures, shaders, rigs, muscles and hair is proprietary.

On a complex project such as Narnia, Clinton recommends all files be routed through a central hub for tracking purposes. Theres a lot of back-and-forth from house to house, and keeping track of which director is on a scene or which version is being used can become confusing. A central hub helps everyone better monitor the progress of imagery and files.

De Quattro emphasizes that studios using multiple vfx houses should think carefully upfront about whos doing what. Its one thing to share assets, its another to share shots, she suggests. While the former will occur with increasing frequency, the latter is something most houses would still rather avoid.

Setting Standards

In addition to resolving scheduling issues, companies need to set up technical guidelines as soon as possible for sharing digital data. The only information that can be shared directly among houses with proprietary technologies are OBJ geometries and images, which can be sent back and forth in exchange formats such as Kodaks Cineon or Sonys OpenEXR. Theres always some sort of translation or conversion that needs to be done, says Cliff Plumer, chief technology officer of ILMs parent company, Lucasfilm Ltd.

Just getting the image formats to work was a little issue, adds Westenhofer.

Outside of general geometries, other 3D information such as textures, shaders, rigs, muscles and hair, which are created by each house using its own technology, cant be shared directly, although houses can pass along some non-proprietary data to help another house replicate a characters look.

For example, Rhythm & Hues and ILM shared some characters in the battle sequences, for which Rhythm & Hues gave ILM the models in OBJ format, along with texture maps, pre-lit turntables, designs and MoCap data. ILM was able to use this information as a guide to make its work look as close as possible to Rhythm & Hues depictions.

Matching colors on shared shots is a particular challenge. Each vfx house, and each DI house, has its own internal colorspace and its own proprietary look-up tables. What is set as a standard becomes pretty paramount, Westenhofer stresses.

The process for Narnia began with each house doing a film out of the same piece of film and scanning it. They then compared the footage and the respective scanner settings, and came up with equations to calibrate the three houses colorspace. While the calculations worked for the most part, it was a big conversion, and a big color shift, adds De Quattro.

Different houses colors ended up looking a little different from each other when they went into DI, requiring another round of calibrations to ensure consistency in the final output. What started as a minor annoyance became pretty much a bugaboo throughout the entire process, Westenhofer recalls.

When working closely with the competition, the key to everyones success was to put the project first.

Farrar notes that the color problems werent unexpected. Color issues are one of the top issues, no matter how [a scene] is shot, he says. Beyond the technical stuff, theres a lot of artistry involved. Satyrs wearing dark leather and centaurs with dark-colored fur were fairly easy to get right, he adds, while brighter characters like grey wolves and blondish cheetahs were trickier, showing a tendency to go blue or red. Those were the most persnickety colors.

Similarly, in shots taking place in external daylight, such as at Aslans camp, ILM was able to add its characters without much trouble. But in the scenes at Cair Paravel, where Rhythm & Hues created Aslan on a greenscreen and ILM added the rest, the colors didnt look exactly right, with Aslan taking on a greenish cast. Its very hard to make color judgments without all the pieces there, Farrar continues.

Executives at all three houses that worked on Narnia stress the necessity of setting up technical guidelines as early as possible, even recommending that if a studio sees the slightest chance of using more than one vfx house, it should set up guidelines that can be distributed to any house that comes on board later. In a best-case scenario, all the houses would be assigned their responsibilities early, so they can begin the critical process of testing as soon as possible.

It also should be remembered that not all guidelines are technical. You need to set standards not just for technology, but techniques, explains Plumer. Starting with a common terminology is important, for example, as is implementing a common system of measurement.

Putting the Project First

Narnia required the collaboration of three top vfx houses, which normally compete with one another on a daily basis. "The most surprising thing was that it went as smoothly as it did," says Clinton. "There's always going to be competition in business and visual effects is no exception, but we're all professionals and the quality and success of the project will always take precedence."

While that competition limits the amount of information that can be shared, all three put the project first and divulged what they could to make it succeed. The collaboration was really great, says Farrar. We all want to do the best technical artistry we can do, and to do whats best for the movie. Theres really a great spirit of cooperation.

One thing that is certain is that studios will increasingly dole out VFX work to multiple houses and that, as a result, more digital asset sharing will occur. Its more the norm to work on pieces of large projects, Plumer says. This issue is going to take up more and more of our time.

And it will be a long while before the industry develops and uniformly accepts additional standardssuch as 3D exchange formats or neutral pipelinesto make asset sharing easier. Nobodys working with another competing shop to develop standards, Farrar says. Theyre running exactly in the other direction.

Karen Raugust is a Minneapolis-based freelance business writer specializing in animation, publishing, licensing and art. She is the author of The Licensing Business Handbook (EPM Communications).