The clouds were modeled in Maya, then brought into Houdini, voxelized and then finer detail and density were attained through volume shaders.

The key for the CG planes, meanwhile, was lighting. Mr. X's pipeline includes image-based lighting. They took HDRI images that were used to illuminate the airplanes. And in some of the sequence they had some interactive lighting: for example, when Vega flies through the storm. These were rendered in RenderMan.

For the CG water in sequences when Amelia flies the Cessna, they had to show believable interaction between aircraft and water. "So we had to proceed with a semi-practical solution," Zielinski adds. "We had a model airplane that flew for our hero plane and later on in the process we painted out the model." Shooting the scenes with the Cessna provided the basic water interaction for the final shots, which was augmented with CG water splashes and spray.

"Because of our expertise in CG technologies, we know what can be done, both technically, and in terms of the budget," Zielinski concludes. "This way we can help the director extend her creative vision through well-placed visual effects. It works because we approach the work the same way they do -- as filmmakers."

Bill Desowitz is senior editor of AWN & VFXWorld.