Epic Effects

The critics have not been kind to Ridley Scott's film Exodus, but none deny the visual effects.

Once Moses leads the Jews away from Egypt and out of slavery, the spectacle begins in full force. There are plagues of locusts, frogs, and flies. Thousands of people. Crocodiles. Dramatic chariot races on the edges of cliffs. And, of course, the parting of the Red Sea. In the past, biblical epics relied on sets and thousands of extras. For this film, Scott relied on crews of thousands who created the cinematic illusions with computer graphics.

Peter Chiang from Double Negative (DNeg) was overall supervisor, managing the work at DNeg, The Moving Picture Company (MPC), Method, Lola, Pearless, and Scanline.

MPC had worked with Ridley on Prometheus, so it tackled the toughest shots, finishing the work from when the Hebrews are released until the finale, Chiang says. They also used their Alice software to create the battle. DNeg handled the plagues and the Egyptian landscape. Lola did the landslide. Pearless did greenscreen set extensions of live-action sets. Method did a lot of skies and some one-off shots. And, Scanline helped MPC with the water simulations at the end, since MPC uses their Flowline software.

DNeg and the Plagues

For the plagues, Scott wanted each to seem plausible in nature, yet dramatic.

He wanted the plagues amped up to 11, Chiang says. But, if you look at YouTube footage of locusts, it's quite underwhelming, so we multiplied the particles and amount that DNeg was doing. And frogs surged like a football crowd through a narrow gap. We had to create that dimension so when seen from a height, they wouldn't look like a flat carpet layer.

Some of the frogs were real. When asked how many frogs they'd need to film, Chiang requested 400.

I just picked a number, and lo and behold there were 400 frogs on set, Chiang says. They came in a bucket. After every take, we had to pick them all up and count them. Ridley, Dariusz Wolski the DP, the set dressers, the animal wranglers. We all joined in. The frogs went everywhere. It was harder picking them up than filming them. I'm glad I didn't ask for 1,000.

During another plague, this one with flies, Scott wanted great vistas of Egypt seen through a wide-angle lens.

In true scale, you wouldn't see the flies because the depth of field put them so far away, Chiang says. So we had some [CG flies] bouncing on the camera lens, and to make others read, they ended up the size of rabbits. You don't notice the cheats as the images flow from one cut to the next. But, if you would look at the 3D scene closely, you'd see that it's full of cheats, speed changes, and sizes.

Of all the plagues, Chiang found the crocodiles most difficult.

All that water, he says. We shot the film in native stereo, so we couldn't do any 2D cheats. We had to respect the Zed space. So those shots are mostly digital. The flow of the Nile and the water interaction with the crocs is all CG. The odd splashes on the people are real, though. Special effects made a boat that could sink with a gimbal that we shot against a bluescreen. To create those shots, the crew at DNeg used a fluid system based on Side Effects' Houdini.

MPC: Crowds and Water

For its part, MPC artists in Montreal handled the Battle of Kadesh sequence by extending environments filmed in Jordan's Wadi Rum mountains and adding digital crowds of soldiers to create the Battle of Kadesh.

These are the same mountains Ridley used for Prometheus, says Max Wood, CG supervisor at MPC. So that was great for us. We had photogrammetry of the mountains already and lots of reference.

MPC's London-based crew moved the crowds through deserts, mountains, and to the beach through an additional nine sequences, and created the Red Sea.

Although the water shots represented the bulk of the difficult work at MPC, crowd shots dominated the work as a whole.

Our biggest crowd had 200,000 agents, Wood says. We hoped we would break our record of 250,000 agents in World War Z, but we didn't get a plate that was wide enough.

Alice, MPC's proprietary system, managed the crowds, whether birds, animals, or people.

We had a lot of birds, tens of thousands of birds, Wood says, seagulls mostly flying around. We thought we could use elements, but there were so many, we did them all in CG. And, this was the first time we had crowds of horses and chariots.

To derive performance data from the horses and chariots, MPC worked with Audiomotion Studios in Wheatley, UK. MPC provided the CG skeletons; Audiomotion handled the motion capture at an equestrian center near London.

We had two horses pulling a chariot with two people in back, Wood explains. We had special suits built for the horses. Audiomotion captured everything - the wheels turning and other elements on the chariots. We had captured horses for other films before, but never two running with chariots. There was a gap of only eight to 12 inches between the horses, so there was a lot of shadowing, but Audiomotion did a great job. They cleaned up the data and sent us clips quickly.

Motion cycles included data for straight passes, left turns, right turns, acceleration, and shots of riders pulling on the reins.

We blended those set pieces together in Alice, Wood says. The difficulty was that horses are left- and right-footed, so we had to make sure the blends had the two horses running with the same stride.

During one sequence, a cliff collapses, sending riders and chariots down the side of a mountain. The filmmakers shot the sequence on an abandoned roadway carved through mountains in the Canary Islands. MPC artists extended the mountains, collapsed the cliff, and added the animated digital soldiers, horses, and chariots. Kali, MPC's proprietary rigid- and soft-body solve

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