Pixar found that the requirements for fur were far different than anticipated. The animators discovered it was advantageous to use less fur, but make each strand thicker on the background rats.

"Also, we had this new project called 'Collisions.' We really wanted the characters to interact with their environments and with each other. If they shook each other's hand, they would actually squish. Or if they were leaning against a wall, their body would squish. Or if they hugged, they would collide with each other. There were methods to do that in the past using simulation, but we wanted to see it in the camera while we were animating so we could control the shapes. So we created software that cheats the collision, where you push into the mesh and it inflates a [bulge] around whatever shape you're trying to push into and that slides around with the character. This way the size and shape of the bulge doesn't have to be a surprise after the animation is done. That helps subtly throughout the film. When Remy grabs a saltshaker, for example, it pushes into his body.

"We also made a few tweaks to facial rig from The Incredibles: we had controls to squash-and-stretch the pupils on the eyes better. The cloth was more complex here and the team made more advancements since The Incredibles, even the way they shade, including the stitching. Someone found an old textile machine manual on how to sew fabric, and they actually ran a simulation of the same pattern from this guidebook and came up with incredible textures and seams. We were able to animate just about anything and then send it to the sim department, and they were able to put clothes on things that went beyond anything [we tried before]. Now because of the collisions, there were no cloth restrictions and animators were able to create movement more freely."

As for fur, it turns out that the requirements were far different than anticipated "When we put the fur on the rats, because everyone loves the technology of that moving fur, they had it overlapping, and suddenly you get the Godzilla factor when the rats are jumping up and down," adds Walsh. "So they kept dialing it down and dialing it down until those poor fur guys ended up turning off the fur overlap. To our surprise, we found that when it gets down to that small a scale, the fur isn't that long and didn't need to be simmed, unless there was collision going on." Also, it was advantageous to use less fur but make each strand thicker on the background rats.

In terms of increased computational power, Pixar was also able to take advantage of a new partnership with Intel. The use of Intel Xeon processors with Intel's Core micro-architecture technology in the servers and workstations provided the superior computing performance behind the scene rendering of Ratatouille, helping to create never-before-seen advances, including lifelike bubbles, innovative lighting techniques and ultra-realistic dripping water effects.

One of Intel's earliest engagements with Disney/Pixar was helping optimally compile their RenderMan software for Intel architecture. One aspect of the optimization was enabling the software to take advantage of instructions added to Intel processors to better run RenderMan's workload, resulting in a 30% in software performance improvement.

A more recent engagement involved helping the Disney/Pixar RenderMan product team to thread their software to make better use of multi-core processors, dramatically increasing the performance of the software on Intel processor technologies from 2-3 to 5X depending on the number of cores.

The studio came up with a new brick map scheme that simplified 3D representations of the environment for each shot. It worked well for the accuracy and soft patina needed, and was helpful with all the kitchen reflections.

Although Pixar was able to take advantage of PRMan 13, containing the new multi-threaded super fast renderer with built-in ray tracing, it had to create several customized tools, primarily for greater control.

To optimize rendering time, the studio came up with brick maps: simplified 3D representations of the environment of each shot. Ray tracing is done from this stand-in instead of the shot's "real" environment, using an in-house technology called "Trace Radiance."

"We knew we didn't want the super sharp, ray traced reflections that we had on Cars," explains Sharon Calahan, director of photography/lighting. "We couldn't afford to make them soft enough and they looked a little too gritty. We couldn't get accurate enough reflections with our old environment map technology, so we did a brick map scheme that worked really well for both the accuracy and soft patina that we needed. This is not shiny, bright, in your face. It's richer and subtler."

This was particularly helpful in dealing with all the kitchen reflections. "The weird thing is, if you do brute force ray trace reflections, as they get softer, they get more expensive, which is obviously not acceptable, so we came up with the Trace Radiance solution to basically keep the render times more reasonable and cut some corners visually that you wouldn't notice," adds effects supervisor Apurva Shah. "For example, the use of simulation for set dressing to create a plate or a dish."

Pixar also came up with "Scatter," an improved subsurface scattering system that gives the artist control over where light energy travels once it penetrates a surface and how its color changes in the process. "Subsurface scattering worked better and faster and we had more control than on The Incredibles," Calahan adds. "We also took gummy stuff on Finding Nemo for fish and tuned that up and made it more robust and provided more control for the lighters. We had a gummy pass that we used for translucency as well as the subsurface scattering."