|The recently-released, groundbreaking production of Avatar routinely required new techniques to be invented — sometimes on the fly — to fulfill director James Cameron’s uncompromising vision. In fact, says David Stripinis, lead virtual camera operator on the film, the blurring of boundaries between pre-viz, production and post led the crew to coin a new term: pre-pro-post.
Stripinis recalls one occasion where an object called a Daisy Cutter was on the day’s filming schedule, but no model of it existed. So he opened Luxology’s Modo 401, quickly created a simple model with material colors but no textures, and imported it into Autodesk’s Motion Builder for the shot. A concept artist later refined it into a finished model, which is normally a pre-production task. From there, it went to production for the creation of a physical model, and finally to post.
“I’m really looking forward to where the technology is going to go, as it links up heavy post production stuff in realtime,” says Stripinis. “Being able to manipulate assets in realtime is incredibly valuable for a director. The director no longer has to turn his baby over to a bunch of nerds in an office and then look at it in four weeks only to see that something is wrong.”
Although the movie takes place in a virtual world, LA-based Giant Studio’s proprietary biometric motion capture system allowed Cameron to direct and shoot multiple mo-capped actors on an elaborate virtual stage as if on a live-action set. All elements of the shot were combined in realtime, as Stripinis and other virtual camera operators — including Tyler Thomson, Dan Fowler and Ignacio B. Peña — “drove” through the virtual world.
The virtual camera, which is essentially an LCD monitor with motion capture markers on it, could move gymnastically in ways no physical camera could. Movements could be scaled by 5X or 10X, so a move of one foot equaled 10 feet. By scrolling the camera upwards from the floor it became a 30-foot techno-crane. Because Cameron liked to fly quickly around the virtual set, Stripinis ultimately accommodated him with a camera-mounted joystick.
“We used to joke that the hardest things in the world were incredibly easy, and the easiest things in the world were incredibly hard,” Stripinis says. “We could take an entire mountain and move it five miles without a problem. But if we wanted to break a branch off of a tree, we couldn’t do it, because the tree is one solid set of polygons.”
A virtual camera operator is, to some extent, a jack-of-all-digital-trades. In addition to driving the camera, Stripinis and his crew routinely manipulated models, characters, and details on the set to perpetuate the live action filming aura. They applied motion capture signals from the set to rigged characters loaded in Motion Builder, whether those characters were the Na’vi or human beings that would later be replaced with live action or digi-doubles. Then, like digital makeup artists or prop masters, they stepped in with the right tool when something went wrong.
Two of Stripinis’ main utility tools were Modo 401 from Luxology and Adobe Photoshop. He relied on Modo for everything from quick models to importing/exporting fbx files. “I like Modo because it has really good versatile tools and I can leave it up and running without using any system resources.”
Stripinis recalls being on stage with digital effects supervisor Nolan Murtha when they encountered a car model that had problems with its normals when opened in Motion Builder.
“Someone had obviously built the left half of the vehicle, and then mirrored it over to the right side,” he says. “It looked fine in the program they used to create the asset, but Motion Builder is extremely particular about the normals, and its lighting system is vertex-based. The left half of the car was lit correctly, while the right half was completely and utterly fubarred. So I launched Modo, loaded the asset, flipped the normals, and it was ready to go.”
After Avatar, the workflow for virtual world production will never be the same, and Stripinis lauds Cameron’s vision and determination in creating a director-driven process. “It shows what someone of indescribable imagination and will can accomplish. It takes pre-viz to a whole new level, because it’s basically giving you frame-by-frame concept art. You’re not left with any ambiguity as to what the director wants.
“We worked really hard, putting in long hours on this film for a very long time,” he adds. “And the thing that really kept us going was the knowledge that we were making something special. At the end of the day, I knew that we could do no wrong, because there was no right way of doing it. No one had ever done this before. So there’s some responsibility there, because what you’re doing sets the bar for all that follows. Hopefully, people will pick up the baton where we left it and move it forward.”