Sinbad Sets Sail on a New Journey into Water Surfaces
A look back at the building blocks
For Doug Cooper, who was a 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 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."
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.
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 very graphic style.
Looking ahead to Sharkslayer
Bill Desowitz is the editor of VFXWorld.
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."
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