Puss-in-Boots Breakdown Shots: (1) Red-green-blue icons represent animation joins in a wireframe view; (2) lo-res “stand-in” models allow for realtime feedback; (3) hi-res model is smoothly deformed into the final pose; (4) Finished scene.

To achieve this, PDI built upon the fluid dynamic systems that were first developed for the studio’s 1998 debut feature Antz, (a film for which Bielenberg was also visual effects supervisor.) The system, which won PDI scientist Nick Foster a technical Academy Award, enabled the studio to animate dozens of layers of water elements. The process entailed animating particles for the waves as well as various splash layers on top of them. PDI leveraged a lot of the water effects work that the company did last year for Universal Studios’ special venue stereoscopic film Shrek 4-D. Bielenberg notes that, “The difficulty with a stereoscopic film is that you can’t cheat as much. On Shrek 2, whenever we could cheat we did cheat! We’re not purists in any sense of the word. We’ll do whatever it takes.”

In the original Shrek, one of the most difficult tasks was creating a glass of milk, but that’s changed this time around. “We have some big vats of milk getting dumped out,” says Bielenberg. “We also have a boiling cauldron with a potion that’s supposed to have a magical yet believable look — glowing and with some translucency.” This time, instead of a glass of milk, there’s volumes of potions spilling across the screen — volumes on the order of The Sorcerer’s Apprentice.

The Crowning Achievement
“Of all the advances on this film, I think that our use of global illumination was the biggest technology breakthrough,” asserts Bielenberg. “Ray tracing/global illumination/radiosity techniques have been out there for a number of years, but it has been price-prohibitive to utilize them significantly. For Shrek 2 we used global illumination for 80% of the shots.”

PDI spent a lot of hours getting the hair to look and move realistically.

“It’s our own renderer, and it’s been re-written since the first Shrek. We developed a bounce light technique that —given a key light — automatically computes the correct bounce light off of the other objects in the scene. If the light bounces off of a yellow wall, it will bounce back yellow in character. When our lighters started using the tool, they would try to work the way they normally do, but once they got used to it, they had to re-think the way they lit things. Instead of thinking that the bounce light was just the icing on the cake, they would start off with a key light and then turn on the bounce light and see what they would get from that. Then they would add additional fill light and tweak it from there. The bounce lighting became a primary lighting tool.”

Bielenberg notes, however, “We’re not just using it as effects lighting — we’re using it to soften the overall feel of the shots. It gives a really rich, soft feeling. A lot of times with Shrek we had trouble with creases under the chins of our characters — it was hard to get light up under there. This way we can get a nice soft bounce light that’s built in to the problem areas. It has a dramatic effect on the visual complexity.”

The Road Ahead
After two-and-a-half decades in business, PDI has seen the CGI industry come of age, and the studio’s successes with Antz and Shrek positions it to stay on the leading edge of technical development. When Bielenberg looks forward, he offers the opinion that “The curve is starting to level off as far as all the ‘Holy Grails’ of hair and water and fire. For example, since Shrek we’ve come up with new techniques for better looking, more realistically animated individual flames and a more interactive approach to lighting them. So I think a lot of challenges have reached a certain level of being tackled, if not solved. I think it’s more about refining everything so that we remove further creative roadblocks. The point of technical development is to remove any constraints on the creative process.”

From his perspective as a supervisor with a more global role on PDI/Dreamworks’ films, Bielenberg expresses some amazement at how we’ve come to take sophisticated techniques for granted. “I haven’t been hands-on in so long, that if I had to actually sit down and do them, I’d have no idea how!”

Ellen Wolff is a Southern California-based writer whose articles have appeared in publications such as Daily Variety, Millimeter, Animation Magazine, Video Systems and the Web site CreativePlanet.com. Her areas of special interest are computer animation and digital visual effects.