The film boasts some of the busiest, most populated shots ever rendered for a CG film. As a result, new software was developed that generated low-res, coarse level-detailed characters. 

"When we started animating we couldn't do the things we needed to do -- show crowds of animals and millions of blades of grass stretching to the horizon. But our people put their noses to the grindstone and made it happen."

A now flat-nosed Scott Peterson is the film's effects head. "Grass -- that was a big one," he said in a reflective voice. "The African plains are vast, big vistas, where you can see a couple of miles out. Our challenge was to fill those plains with grass and do it in a way we could manage.

"We designed a tool for the layout department that would distribute grass by positioning geometric chunks of it in a shot. From there it went to the surfacing department where they handle its density: how it clumps, how scraggly it looks. They add accent grass and come up with the overall texture.

"Then it goes to the lighting department. They had to develop tools that would regroup those chunks of grass into layers that make it easier to render large amounts of geometry. The surfacing department had to come up with a way of changing the grass' density -- have it very detailed when it's close to camera and more coarse as it get further away, but do it in such way that the audience doesn't notice the transition. We spent some time implementing that, making it efficient and coming up with intuitive controls for them to set up.

Clouds were a great challenge. A library of geometric cloud shapes was used to rough in their location and shapes before becoming transparent and translucent.

"On the rendering side, one of the ways we fixed the 'buzzing problem' [between the grasses' differing textures] was from a trick I learned at SIGGRAPH. It was the same one they used to fix King Kong's fur, which was to make the grass transparent as it gets skinnier -- it makes it blend better."

Madagascar: Escape 2 Africa boasts some of the busiest, most populated shots ever rendered for a CG-animated feature. "We did spend some time on that," Peterson casually added. "We have probably the largest crowds and amount of crowd shots than any of our films by fairly significant margin.

"The way we addressed it was to create a separate department just to handle the background animals. If there are more than 10 animals onscreen we call it a crowd shot. The challenge was how to mix and match the different animals and the variations within each species in believable ways. Scattering them randomly doesn't work right: we needed to choose the right height for each animal to compose a shot.

"We developed new software that generated low-res, coarse level-detailed characters. We can put roughly a thousand of them in a scene for the same cost as 10 or 20 hi-res ones."

That software faced its biggest challenge in the scene where zebra Marty tires of being part of a herd of thousands of near look-alikes. "We had 12 or 24 basic stripe patterns, plus eight different body and head combinations," McGrath recalled. "We blended them to get what looks like infinite number of zebras, all very subtly different."

Giving them all Chris Rock's voice was a bit of challenge as well. "Chris recorded every voice for them," Darnell continued. "Skywalker Sound did great work, varying the pitch slightly for each one. That shot went on for so long we didn't have enough audio of him to cover it all the way through. We wanted it to sound like a million zebras talking so they put their hands on every scrap they could find, even Chris talking between takes to fill it out. All the voices blended together so you couldn't hear what he was really saying."

The film's creators are justifiably proud of the effort they put into creating its fanciful, yet realistic environments and filling those massive African skies. "Clouds were a great challenge for us," said Peterson. "One of our toughest problems was how to split up the work between various departments, but even before that we had to help the layout artists figure out how to place clouds in the sky and give them something to work with. We came up with a library of geometric cloud shapes they could use to rough in their location and shapes. Then we figured out a way to give them more detailed texture and turn them into transparent, translucent volumetric shapes.

"We don't have a very mature set of volume rendering tools, so we had to write software to help us break the clouds down into particles. The particle tools were a challenge for us: how do you take a simple shape like a dome or a sphere and turn it into particles that look detailed and have a cloudlike texture?