Step by Step: Night at the Museum: Battle of the Smithsonian

When 20th Century Fox debuted Night at the Museum in 2006, audiences
flocked to see actor Ben Stiller cope with the comic chaos that ensues when museum exhibits spring to life. Now Stiller and director Shawn Levy have returned with Night at the Museum: Battle of the Smithsonian, and they've upped the ante. In one scene set in Washington, D.C.'s National Gallery of Art, Stiller confronts a giant octopus, which he douses with water in a most unusual way.

"The story point is that the octopus is harassing Ben because he's thirsty," says Raymond Chen, visual-effects supervisor at Rhythm & Hues in Los Angeles. "Ben picks up a seascape painting by Joseph Turner, and all the water in the painting rushes out and onto the octopus. Its tentacles start playing with the water, and the octopus transforms from a gray, sickly color to a healthy reddish-purple."

The plate photography for this scene was shot on an elaborate set of The Turner Gallery in the National Gallery of Art, with lots of wooden moldings and framed paintings that appear to be moving. Chen says that at the time of the shoot, the paintings in the gallery were just framed greenscreens. The animation inside the paintings would be added later by the Santa Maria, Calif.-based studio http://www.cafefx.com/ " target="_blank">CafeFX. Rhythm & Hues would animate the water that flowed from the painting onto the octopus.

On set, Stiller actually holds an empty picture frame, according to Chen. "We had a water cannon on the floor behind Ben that would shoot water through the center of the empty frame and onto a painted Styrofoam buck that stood in for the octopus," he says. "We wanted to get some practical water onto the octopus along with the CG water that we would add later. So Ben had to time his swing of the empty picture frame to coincide with the water shooting from the cannon."

The painted stand-in for the octopus was based on a preliminary version of a CG octopus that Chen's team had modeled in Autodesk Maya, and it was quite limited. "The buck didn't have any legs at all," Chen says. "It just had a head and nose structure, which was the only area where the practical water was going to hit. Of course, part of the problem of using that element was that as production went on, we refined our models. By the time we ended up with our animation, it didn't necessarily match the buck very well. But it was great to see a reference of the way that water would splash onto something of that shape. We did end up using some of the practical water in the final composite, but because of the tight interaction we needed between the octopus and the water, most of the water would end up being CG."

Back at Rhythm & Hues, the plate photography was cleaned up using the studio's proprietary rotoscoping and compositing tool, Icy. "In this sequence, there's a lot of interaction with Ben, including having the octopus' tentacles wrap around him," Chen says. "For the part where the water splashing, it was easy to use a clean plate to fix where the buck was, but when Ben is wrapped in the tentacles, we did have a fair amount of roto work. On set, they had rigged green strapping around Ben's arms so we could get that interaction. We covered that up with our CG tentacles." The animation of the octopus was done with Rhythm & Hues' proprietary animation system, Voodoo.

To splash water onto the CG creature, Chen's team used the studio's proprietary fluid dynamics system, Ahab, which earned Sci-Tech honors last year from the Academy of Motion Picture Arts and Sciences. The software employs the idea of energy cascades, allowing artists to achieve the high amount of detail that's required for realistic water animation. This system is ported to Side Effects Software Houdini animation software, and the results are rendered using Rhythm & Hues' proprietary tool Wren.

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"Once the octopus was wet, its surface looked different," Chen says. "We had to create two different versions of the octopus. One of them was the drier, sickly version and the other was the wet, healthy version. We did do a lot of back and forth with the surface qualities to determine how sick to make the dry version look without making him appear dead. Lighting was all done with our proprietary lighting package, Lighthouse, and rendered with Wren." Integrating the creature into the scene was done with Icy.

The finishing touches for the octopus required just the right amount of believable slime, which became apparent once the creature was wet. "We see this slimy layer on its body," Chen says. "When its tentacles touch something and then pull away, there's a slimy residue left behind. So when the octopus pulls Ben into a little hug, it leaves slime all over him. On set, the production had applied some gooey methyl cellulose to Ben, but we had to add a lot of CG slime."

Director: Shawn Levy
Visual Effects Supervisor: Dan Deleeuw

Animated Paintings: CafeFX

For Rhythm & Hues:
Visual Effects Supervisor: Raymond Chen
Modeling: Ryan Smith
Look Development: Dante Quintana
Animation: Michael Holzl
Rigging and Technical Animation: Matt Derksen
Lighting: Duffy Knox
Splash Water Effects: Steven Ong
Slime and Water Spill Effects: Brian Walters
Water Runoff Effects: Anthony Zalinka
Compositing: Behnam Shafiebeik
Fluid Dynamics Algorithm: Dr. Jerry Tessendorf