Disney Goes Open Source with Ptex

Watch a demo of paiting 3D models in Ptex. [1]

Walt Disney Animation Studios (WDAS) has launched an open source site (www.disneyanimation.com/technology [2]), allowing users for the first time to access in-house software.

The first software available is WDAS's acclaimed texture mapping system, Ptex, (http://ptex.us/ [3]). Ptex was developed by WDAS Principal Software Engineer Brent Burley for use in production quality rendering, and is being driven to become adopted widely in the community by WDAS Director of Technology Dan Candela. WDAS has also compiled a set of papers available on the site for sharing additional technical innovations that will benefit the industry.

With the increase in render complexity requirements in animated film, the WDAS team found that standard texture-mapping methods being utilized had become inefficient and complicated for artists to use. In an effort to increase the efficiency and quality of texture mapping on complex and intricate geometry, Burley spent a year developing the Ptex software. Overseen by Candela, the Ptex system has already been licensed to multiple vendors and studios (such as Sony Pictures Imageworks and Weta Digital), and is now utilized on all projects at WDAS.

Ptex introduces a new texture mapping method that has benefits for film production. It eliminates the need for tedious and labor-intensive UV assignment by applying a separate texture to each face of a subdivision or polygon mesh. The Ptex file format can efficiently store hundreds of thousands of texture images in a single file, resulting in a significant reduction in server load. The Ptex API provides cached file I/O and high quality filtering -- everything that is required to easily add Ptex support to a production-quality renderer or texture authoring application.

This, of course, is part of a growing industry trend toward standardization. Imageworks recently released the Alpha version of its source code for its Open Shading Language (OSL). And GenArts, which partnered with Lucasfilm last year, has expanded its software portfolio with recent purchases of The Foundry's Tinder and Tinderbox plug-ins (and with an eye on future Nuke collaboration) as well as wondertouch.

"Probably one of the biggest questions that people ask us is, 'Why is Disney doing this'?" offers CTO Andy Hendrickson. "Part of the open source strategy is that there is a lot of software that a studio builds and a lot of studios build the same exact software over and over, and certain parts of that software are not part of our secret sauce in making images. Certain parts of it make sense in sharing it with other people so we all don't have to recreate the wheel. Now Ptex is one of those that is unique, novel and groundbreaking. But, ultimately, it would be better to share than hold in-house because it helps all of our folks in the industry so much more and we get such good will than keeping it private. So we decided to do that. And in the process, we looked at other pieces of technology, and thought these would be better to share than to keep in-house also. Right now the only other one available is Pythoscope (a unit test generator for programs written in Python), but we're hoping to have a couple more done in time for SIGGRAPH."

Candela adds, "Also, when we open source something, we want it to be a successful project. And we define success by other people using it and contributing back to it. So Ptex went out [in January] and within a few days, there were lots of tiny contributions of getting it to build in different environments. Nothing major architecturally but there is already a community building up around it. And if you look at the open source that's around in the world, 97% of it is dead. Someone put it out there and nothing grew up around it. We don't want to do that. We want to put things out there that will have a life of their own and be beneficial and be used."

Although Ptex was developed during Meet the Robinsons [4] (the T-Rex was one of the assets), all the textures were already painted before Ptex could be applied. Thus, the short, Glago's Guest [5], was the first project to use Ptex, and then Bolt [6] was the first feature to take advantage of it.

"Glago was interesting because it was a small crew that was interested in doing things differently in a much lighter weight way," explains Brent Burley, principal software engineer and creator of Ptex. "And there was somewhat of a rebellion against UV textures in general because of the weight that we had both in human labor and computer resources during rendering, and so the leadership on that show was going to change completely to projection painting, so it's a different UV less painting but it has its own limitations and overhead. But they didn't have a complete projection workflow set up; they were just figuring that out and they had painted some things already and Ptex worked so well that they tried it and switched everything over and used it from then on. And we had some discussions and some very preliminary support in our proprietary painting tool, but I didn't anything for a while and it wasn't until after the textures were all painted that I found out that they used it on everything [on Glago] and it was a complete success.

"I think there was some reluctance to use it on Bolt initially because they were already in full production by the time Glago had finished. And they weren't up to speed to the point where they were hitting all the I/O problems that we had on [Meet the Robinsons], but we convinced them to try it with a backup plan in case everything was crashing and things didn't work like we expected. But then artists started redoing their UVs and once they started to see the benefit -- we had a bug called Unitile that would do an automatic UV of the entire model as a single Ptex file -- everybody started using that. And, luckily, there were never any crashes or any artifacts."

Not surprisingly, Pixar was interested in Ptex as well and now it's available in RenderMan. "And before we released it open source, we pre-licensed it with other vendors and studios and it was presented as a Eurographics paper [in 2008]," Hendrickson adds. "So the formation of it started out as grass roots, but the popularity of it has grown. So a lot of studios are adopting it now or have plans to adopt it."

Candela explains that Ptex has given them the ability to "paint textures onto geometric surfaces easily and is also friendlier on all the systems that serve textures to render farms. It gives us quantum leaps forward in our I/O throughput for when we're rendering and how we serve up data."

Naturally, Ptex is integral to Disney's next animated feature, Tangled [7]. "It's pretty much on the surface of every object," Hendrickson says. "The interesting thing with Disney is that…we have a lot of people who do painting and texture assignment on our geometry is our bread and butter-- it's how we do what we do. And so this technology is an enabler for us and also an enabler for the rest of the industry. It's just good for us to put this type of technology out there so that when people come to Disney when we recruit will know more about what Ptex is rather than having to go through a laborious training session."

Bill Desowitz is senior editor of AWN & VFXWorld.