The previs for the caves and the Akator pyramid at the end were dramatically changed onset by Spielberg.

"The first stuff we worked on was the Area 51 and all the opening scenes in the desert and the warehouse from Raiders," Gregoire recounts. "That was pretty easy for us to do. There is actually a really high-res image of Area 51 on Google Earth, so we were able to build out all of Area 51 from Google Earth. I literally built the lower quarter of Nevada and then used that as a general set for almost everything in that scene, even where he crests the hill in the morning to see the Doom Town over the horizon. In previs land, where Doom Town was placed was the testing ground just west of Area 51, where you can see all the craters on Google Earth. It was just two of us, Clint Reagan [the L.A. previs supervisor] and I. The first sequence I was responsible for was the opening roadster chase, which got picked up for additional changes by [Previs Artist] Mike Comfort later in the schedule when we had nine people on the team."

Gregoire says Spielberg's "approach is to direct us and properly use us as a tool to implement his ideas. A lot of directors and productions will get us to come up with ideas and we'll toss things around, but with Steven, he actually really directs us. The effort he puts in with us is commensurate with the effort he puts in on stage, and that's why he's so successful. He uses us to the fullest extent and it empowers us to disseminate information that's useful to every department."

As for the thrilling waterfall sequence, "that entire thing was planned out to a T so that when [Visual Effects Supervisor] Pablo Helman went down to South America with a unit to shoot the plates, he knew to the altitude how high his helicopter needed to be based on the sea level altitude to get some of those shots. We were able to build those waterfalls based on Google Earth information, Google Earth topography information and then site location photo information to estimate heights, falls and positions, because Steven took those waterfalls and actually reversed them since there are only two levels of falls at this particular location. He took them over number two and number three and then took them over number one as a matter of sequence, so we were able to build the entire falls to scale, block out the entire sequence with Steven and then send Pablo to South America with a specific packet of information, so [he could perform his task more efficiently]."

Previs was used in the speeding jeep/swordfight sequence in the jungle. 

However, the previs for the caves and the Akator pyramid at the end were dramatically changed on set by Spielberg. Gregoire and Previs Artist Ryan McCoy were still doing the finale in trailers with laptops until the end of shooting. "There were a lot of iterations and it was very complex," Gregoire suggests. "The final shot, where they emerge from the blow hole to observe the valley buckling and the pyramid collapsing and the debris spinning around and then the saucer rising up and disappearing and the rocks stopping and suspending and dropping and the walls collapsing and the water coming in, was 20 seconds longer in the previs shot. But it was all there. That was a long, long iterative process with Steven to figure out how he wanted to do it. He'll sit down and start sketching his own boards and they're very rudimentary, but they work. He sees it so well in his head and can draw it so that when I put it in front of an artist, it comes together when they start laying it out in Maya.

"At the top of the temple, when Indy and the others figure out the sand gag and the pile-ons rise, we had an opportunity to use ILM's Zviz with a specific controller for Steven to fly around in and explore. Zviz reached a point where on [Crystal Skull] I was able to move some large sets from Maya into Zviz. ILM had written a driver, which allowed a PS2 controller to be hooked up for ease of camera navigation. It also allowed us to set keyframes for the camera by pushing the X button, create new cameras with the O button and other functions. The Akator pyramid was one place where the system worked well. I was able to hand Steven the controller and let him explore the environment setting camera in and out positions, creating new cameras and directing the scene. I was on the keyboard and mouse as a guardian angel helping him out with higher level controls and moving characters around. We then exported all the cameras and brought them back into Maya and completed the resulting shots. Even though it changed dramatically, there were a couple shots that were faithful to the angles that he chose and it gave him food for thought."

Bill Desowitz is editor of VFXWorld.