DreamWorks Expands 2D & 3D Water in Significant Ways

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Sinbad sails on a long journey for DreamWorks in developing the right CG water. Sinbad: TM & © 2003 DreamWorks LLC. [1]

Prince of Egypt [2], Antz [3], The Road to El Dorado [4], Shrek [5], Spirit: Stallion of the Cimarron [6] and now Sinbad: Legend of the Seven Seas are all heavy into water [7]. In fact, DreamWorks co-founder and animation guru Jeffrey Katzenberg readily admits it: the studio definitely has water on the brain. And wait till next year's Sharkslayer, DreamWorks' gangster-inspired answer to Finding Nemo — it's their ultimate in waterworks.

According to Craig Ring, digital supervisor on Sinbad and lighting supervisor on Antz, water is all over the place in Sinbad and is represented by four approaches utilized on other films. "The simplest thing we've done — and it's surprisingly effective — is to take a painting of water and then do a compositing ripple distortion over that painting," Ring offers. "It looks astoundingly good but only works for very calm water like the surface of a pond." In Sinbad, this occurs, for instance, when the protagonist talks to Marina on the ship at night.

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Craig Ring, digital supervisor on Sinbad. Craig Ring headshot courtesy of DreamWorks. [8]

The second level up the surface water chain in Sinbad, Ring says, has to do with a fluid simulation. "It provides more control over water to make it believable and stylized. It allows you to change the wave shapes. It's great for creating an ocean surface. You just get this nice, complex ocean with big and small waves, and everything in between. But it's a single surface; there are no splashing or breaking waves. We had waves that were 30-feet high on Sinbad. We used it most prominently during the sea monster attack." However, the full-blown ocean simulation utilized on Antz and Shrek, which was inspired by Areté Entertainment's Advanced Fluid Simulator, was not applied to Sinbad because it didn't call for photorealistic splashes.

The third use of water, which DreamWorks previously used in El Dorado and Spirit, occurs during the rushing river sequence involving the Sirens, the mythological women that sing songs, entrance sailors and cause them to crash on rocks and drawn. "It doesn't look like an ocean and it's not calm," Ring suggests. "It is a rapid slashing technique used to create a surface and then send ripples through the surface. You can think of it as a bed sheet when you flip it and you feel a wave moving through the bed sheet even though it isn't moving. You combine that with animated textures that look like a swirl of color and foam. The illusion looks like waters flowing down this river. It was first really pushed on Spirit, when Rain falls into the river and Spirit saves her."

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A lot of work went into combining the 2D and 3D worlds of Sinbad. Sinbad: TM & © 2003 DreamWorks LLC. [9]

As for the Sirens themselves, they were essentially female creatures that look like living fountains. The technique was similar to the one involving the aquatic aliens in The Abyss. When the Sirens rise out of the water, they splash up like a wave, float in the air and then fragment into a million drops of water as they try to sweep the sailors off the ship.

Ring says they were very careful not to show anything risqué on the Sirens. "We pushed the speed and scale a lot during the Sirens sequence. There was this huge wall of rock that everything rushes into. We wanted to integrate 3D with stylized, traditional splashes hitting rock, so we had 2D animators draw splashes, which we texture-mapped onto little cards and emitted these cards like a particle simulation coming off the rocks. Instead of being photoreal, it allowed us to get bigger, more complex splashes than you could affordably draw because we were multiplying that same slow animation hundreds or thousands of times in the shot. But it still has a feel that integrates well with the drawn characters."

A look back at the building blocks
For Doug Cooper, who was the sfx technical director on Prince of Egypt and is the lead cgi supervisor on Sharkslayer, each film built on the work of previous films for specific and unique needs. "The most obvious challenge of Egypt was the parting of the Red Sea sequence. How do we credibly create a massive sense of scale in the water? The intent was to come up with something that looked like a moving painting. We used a lot of painted reference from the art department as well as other pieces of art. We had paintings of stormy oceans that were key. We used very few photoreal or photographic references. We were starting from nothing so had to come up with a whole process from scratch. Other water sequences such as the Nile were done using Alias primarily as an effects package. But the Red Sea sequence was produced entirely in Houdini [10] 1.0 and 1.2 because of its procedural animation capabilities. Most of the masses of water for the Red Sea were animated using surfaces. For those calmer seas, a lot of that was a combination of noise fields and typical fake water for the surfaces. Something we did to enhance the look of it, though, was the development of a shader by Moon Seun, where we took simulation data of calmer, flat oceans that we got out of Areté, and turned those into [texture] maps, which we could then use to displace some of the large scale ocean shots."

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Some water work takes on Biblical proportions. Prince of Egypt: TM & © 1997 DreamWorks LLC. [11]

Cooper adds that this technique allowed them to control and animate surfaces in a very atypical way compared to other packages at the time. But they used no fluid flow or particle simulation for the Red Sea. "We wanted very art-directed motion. When you part the sea, there is no simulation that can do that because it is not part of nature. The animation directors were very specific. 'We want the wave to move this way; splash to occur here.'"

The water walls and parting of the Red Sea were animated with Houdini and rendered with RenderMan. The look of the parting was developed by David Allen, an effects animator now working on Shrek II at PDI. "I worked on the drowning of Egyptian soldiers," Cooper explains. "I used procedural animation and Houdini. I layered in a lot of 2D effects so 3D water wouldn't stand out." As with Sinbad, they plotted out frames of the CG animation onto pegged animation paper, which they turned over to the 2D animators to make traditionally-drawn splashes.

Toward the end of Prince, they developed a rendering technique applied more forcefully on subsequent films where they mapped hand-drawn splash particles onto particle systems with sprites to create big splashes that looked hand-drawn. This allowed for a lot more splash rendered in the computer. Doug Ikeler packaged that into Spryticle, which was an in-house tool used on El Dorado, Spirit and Sinbad.

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Spirit tried to capture a more painted look then the other DreamWorks features. Spirit: TM & © 2002 DreamWorks LLC. [12]

Instead of a procedural animation approach using Houdini, in El Dorado they used Maya to take a very hand-sculpted approach. The animators modeled keys poses of the water in Maya and then used them as blend-shape targets with the help of an interpolation plug-in written in-house. The advantage to this approach was it was more conducive to the style of the art direction, which required very specific shapes and timing of the waves, somewhat akin to digital stop-motion.

Overall, Prince had an almost brush-stroke style. It challenged the animators in what they did with the shaders and textures on the surfaces. On El Dorado, the look was much more graphic, so they had to tune the surface shaders to come up with a different look for that water. And they required different shapes. It was more about blocking of the masses. That's why it made sense to use the sculpted approach. On Spirit, they returned to a more painterly style that was much richer. Sinbad was a return to a very graphic style.

Looking ahead to Sharkslayer
On Sharkslayer, most of the previous techniques are not really applicable because they aren't dealing with water surfaces – they are dealing with a whole underwater environment. "So we add particulate matter, depth queuing and atmospheric haze," Cooper says. "We are working on light fall off and how it changes color underwater. Bubbles and ripples so that when fish swims by quickly they will leave a trail of bubbles and often the water will distort the scenery behind it. Sharkslayer is a CG-rendered look. And we are pushing it more than in previous films, using subsurface scattering and global illumination on a massive scale. This is not photorealistic but believable. It is richer than previous films. We pay close attention to detail in effects too. There is a Whale Wash sequence [a hip-hop parody of Car Wash] with lots of soap suds and bubbles. We cheat on the physics but use the fluid simulation technology developed on Antz and Shrek."

Bill Desowitz is the editor of VFXWorld.