"For every layout, we had the Lidar scan of the jungle, so looking at the footage -- the information about the camera and the lens-- we were able to match the lidar model with the actual live plate. We had the dips in the ground and the trunks of the trees, so it was very helpful for the layout workload but also to create the shadows of the trees on the CG model, to create the bullet impact as the humans shoot the Hounds."

This also necessitated R&D in the creation of a forest generator with Softimage's ICE and various plug-ins. "In many scenes, we had to do some set extensions from the jungle or in some scenes we created an entire CG jungle as well, which we created using ICE again as a quick way to populate a scene with trees," adds Théroux."We had pictures of the jungle and modeled the plants with the same shape and texture; we made a bank of the native plants, depending on the sets, and with our plug-ins, we were able to populate an entire set with the corresponding CG plants, trees and vegetation. Of course, we had to make sure everything could render in mental ray, so these scenes were very heavy.

"And we have a long traveling shot where it goes from a lake and flies over some people and goes up a cliff and we end up in the camp of the Predators. And we had to create an entire jungle to match two plates together. The beginning and end were live but everything in the middle was CG. No matter how good the animation was, if the interaction with the jungle wasn't believable, you never would've believed it was shot there with the plates."

Meanwhile, augmentation was done on the Predators, too, including blood, light simulation (muzzle flash, plasma blasts, sparks and laser) and cloaking effects (transparency and transition) were achieved in CG using different combinations of RealFlow, 3DEqualizer, Flame, Smoke and Fusion.

"The look of the Predators is different all the time because of the transitions and cloaking and uncloaking," Leduc says. "We did a lot of work on this style."

Bill Desowitz is senior editor of AWN & VFXWorld.