The original mandate for Crystal Skull was to resist much CG, but things changed slightly once Steven Spielberg got on the set. Above is the temple exterior. All images ™ & © 2008 Lucasfilm Ltd. 

Remember when Steven Spielberg and George Lucas cautioned about the limited role of vfx -- particularly CG -- on Indiana Jones and the Kingdom of the Crystal Skull (now playing from Paramount Pictures)? The primary objective was to emulate the iconic look and feel of the three previous Indy movies shot by Douglas Slocombe.

However, while the filmmakers remained fairly faithful to their original mandate, the final results required more CG than anticipated. But that's a Steven Spielberg movie for you: once he gets on set, the situation often changes.

"The original premise, even from the first meeting with Steven and George, was to have this one blend in with the other three: to have the same look, the same lenses, the same sense of reality," confirms Pablo Helman, the visual effects supervisor who previously oversaw Munich and War of the Worlds for Spielberg.

"And we did do that. Even though they don't do matte paintings on glass anymore and there's a fair amount of CG, we did take a look at how the other movies were done and the sensibility about geography in the same shots as the mattes. We also followed whatever Steven was doing on the set, including his signature shot compositions and how he marries characters and performance and geography into one epic shot. We carried that into the visual effects.

"It's really scary when you think about it because you didn't know how Steven was going to take this thing on. Once we went on location, we saw him doing what he does best, which is getting inspired at the spur of the moment. From there, things started changing, including how the work was divided. When we were shooting the Doom Town [military test sequence], for instance, there was a lot more CG than you might think. But what you probably didn't realize is that Doom Town is a miniature with a lot of 3D matte work. The Digi-matte department photographed everything so they could build digital sets, since it's all blown up later. There was a lot of second unit work originally planned for Doom Town, which became principal photography once Steven decided to turn the camera around. This became a very organic process for all of us."

Organic is the key word because this '50s-era Indy adventure that takes place during the height of the Red Scare features quite a variety of visual effects: Digital mattes, 3D digital mattes, extension work in the jungle and water falls and temple sequences, as well as plenty of creature animation, including prairie dogs, monkeys, ants, digital doubles and aliens. In all, there were 560 vfx shots and 48 minutes of screen time because Spielberg wanted longer takes. There were also around 300 artists working for eight months at ILM's office in San Francisco's Presidio.

"The most important part of the R&D had to do with particle work," Helman continues. "For Doom Town, there was smoke on the houses, dust and the explosion. In the opening warehouse, there is the gunpowder. The rocket sled had some particle work, but the fire in the back was real at Steven's insistence to get more texture. Inside the temple heart at the end, where the room rotates and breaks away, there was more particle work. And also there is debris surrounding the saucer at the end. So we revamped our fluid engine derived from PhysBAM [now called 'The Brain.'] The engine can do water, fire, explosions. In this case, all the particle work was creature intensive, which required a new approach. The entire temple environment is CG along with many of the characters." In fact, Helman is pleased that the fourth film in the franchise comes full circle in terms of its supernatural climax.