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Computerworld - Director Peter Jackson's Lord of the Rings films end with an epic battle on-screen. Behind the scenes, however, another struggle was under way. As each movie in the trilogy went into production, visual effects studio Weta Digital Ltd. scrambled to add the processing power needed to render an increasing number of computationally intensive special effects shots.
By the end of the three-part project, the Wellington, New Zealand-based company had built a massive, 3,200-processor 3-D rendering server farm to cope with the load. The installation is ranked on the Top500 supercomputer list as one of the world's largest supercomputer sites. With some 2,400 of those processors residing on blade servers (and the remainder on 1U, or 1.75-in.-high, servers), it's also one of the most compact.
Weta and other visual effects studios are rapidly turning to large clusters of blade servers, often running Linux, as they balance the need for more processing power with the desire to minimize costs and maximize the use of valuable floor space.
Special effects are playing an increasingly large role in movies because audiences want them, says Greg Butler, digital computer graphics supervisor at Weta. "Film audiences expect visual effects to keep blowing them away. The only way this is possible is through the constant upgrading of our infrastructure," he says.
With the Lord of the Rings trilogy, the number of visual effects shots started at 540 in the first film and roughly doubled for each of the next two movies. Industrial Light and Magic (ILM) in San Rafael, Calif., faces similar pressures. "In the first Jurassic Park movie, we did 75 shots. Now, with a Star Wars movie, every shot has some effect in it," for a total of 2,000 to 2,500 shots per film, says Chief Technology Officer Cliff Plumer.

Complex visual effects like this battle scene from The Return of the King can require more than 30 rendering passes per frame. Image Credit: New Line Productions Inc.

The processing power required to render even a few shots is significant, says George Johnsen, chief animation and technical officer at Threshold Digital Research Lab in Santa Monica, Calif. "In the visual effects business, there's no end to how many computers you can use," he says. A single shot can range from a few seconds to several minutes. Each second of film includes 24 frames, each containing up to 4,996-by-3,112 pixels in 32- or 64-bit color. Separate passes must be made for each object that requires rendering in the frame and for attributes such as texture, lighting and