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Magnolia: A Surreal Storm

Feb 1, 2000 12:00 PM, Ellen Wolff

Of all the twists in the nine-pronged plot of New Line's Magnolia, none is as startling as the pestilence of Biblical proportions that caps the film. During a sequence composed of dozens of shots, thousands of frogs pour down from the sky. At first, it appears that just a few frogs are being flung past the windows of various cars and homes. Then suddenly, in an exterior view of a swimming pool at night, the staggering scale of this surreal event is revealed. Six thousand frogs rain into the glowing pool-wildly splashing, bouncing off the diving board, plummeting into trees, and wriggling in masses on the ground. The task of animating this torrent of CG frogs fell to Industrial Light + Magic.

"The swimming-pool shot was what we spent the most time on," says ILM's Joe Letteri, the film's visual effects supervisor. According to Letteri, director Paul Thomas Anderson wanted the shot to hit with overpowering impact. "He thought of this as another character arriving late in the film, which is a tough thing to do," Letteri notes. "Paul wanted something uncommon-not just an earthquake or tornado-because this wasn't meant to be a disaster per se. He could have done a hailstorm and hit all the beats, but he wanted something both real and unreal."

During plate photography, special effects supervisor Lou Carlucci had rigged the trees to rustle, the diving board to bounce, and the pool water to splash, setting the scene for the CG that ILM would add later. Using this plate, Letteri first did rough choreography in Maya to figure out the density of the frogs and where to place them. His team created low-resolution, roughed-out, shaded frog shapes to get a sense of scale and depth. "We were looking at things like speed," he explains. "We knew what the speed of a falling bullfrog should be, but how would that photograph? Would we need to cheat the speed? We used Maya for testing concepts like that."

They learned that they did have to cheat. "We assumed these frogs were coming from a cloud a few thousand feet in the sky. If the frogs really were falling as fast as they should be, they'd just be streaking through the frame and they'd motion blur so much that they'd just look like rain. Rather than cheat the speed, we just 'dropped' them from a lower height because we wanted to keep the physics correct," Letteri elaborates.

The next step was refining the collisions and determining where specific elements would hit. "During the plate shoot, Lou Carlucci had fired pellets from air guns filled with a little bit of stage blood, so that splattering was done practically," notes Letteri. "And the water splashing out of the pool was real water, so we timed our frogs hitting the pool to that. But everything that was hitting the ground, and the splashes hitting the diving board, were things that we had to add digitally."

ILM employed both keyframe and procedural animation techniques using in-house dynamic simulation software. This allowed the team to generate massive numbers of frogs efficiently and tweak individuals as needed. "When you have 6,000 frogs in a shot, it ultimately comes down to having the dynamics be procedural as much as possible," says Letteri. "But you also know that the director is going to look at some frogs hopping around over in one corner and ask you to fix them. Those were done with hero animation in Softimage. The dynamic simulation proved remarkably complicated, just because of the force of the impact we were trying to achieve. So, in some cases, we actually did some things that looked like they were done with dynamics but were done entirely by hand. And sometimes we had to go in and fix some of the dynamics by hand because we just couldn't get everything to calculate properly. These frogs were traveling at 100mph and stopping in an instant, so it took a lot of calculating to get it right. Ground contact is the important thing, and here that contact happens well within one frame. Normally, we have the luxury of calculating things frame to frame."

A particular challenge was making the numerous CG frogs convincingly touch the ground. "You always need to lock an animated character to the ground," notes Letteri. "You usually lock the feet down, and then all you have to do is lock down where the character is. Here, we had to lock down every corner of the frame because no matter where you looked, there were frogs on the ground."

Despite the fact that no single frog is scrutinized closely during this shot, Letteri says that ILM spared no detail. "They were modeled in Alias, and we used our Viewpaint software to paint them," he states. "They were fully enveloped and had all this simulation when they moved. We also created details in our shaders for RenderMan so that we didn't get any repetition. There were lots of details that we didn't get to use, but we treated them as if Paul was going to ask us for a close-up on one of them." To avoid a rubber-frog look and ensure that the frogs conveyed a sense of life, ILM animated occasional "survivors" that climbed over their less-fortunate buddies. "We wanted you to feel that these were living animals this was happening to," says Letteri.

He admits that rendering took a while because of the sheer number of frogs and dynamic calculations involved. He also says that the final step, compositing the frogs into the plate, was complicated by photographed steam rising from the pool. Removing and replacing this steam required a combination of tricky extractions and roto mattes.

But Letteri says that the overarching challenge came from Anderson's increasing expectations. "Once we started working, Paul wanted to make it bigger. We wound up doing about double the amount of frogs that we thought we'd have. I think Paul realized that if you're going to put something like this up on the screen, you'd better make it memorable."

Paul Thomas Anderson - Director Robert Elswit - Director of Photography Lou Carlucci (Effects Concepts) - Special Effects Supervisor Steve Johnson (XFX Group) - Frog design For ILM: Joe Letteri - Visual Effects Supervisor Camille Geier - Producer Gregor Lackner - CG Supervisor Greg Maloney - Compositing Supervisor Paul Griffin - Animation Supervisor

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