The realistic oceans in this summer’s movies, including Poseidon, are CG simulations courtesy of cutting edge advancements from Industrial Light & Magic and Scanline. Photo credit: MPC. Unless otherwise noted, all images © Warner Bro

... But not a drop to drink. Why not? Because it’s all CG!

When you go to the theater this summer, you may wish that you had brought a life vest. But no need for panic. The oceans you see on the big screen in Poseidon and Pirates of the Caribbean: Dead Man’s Chest, no matter how real they appear, are still CG simulations — albeit spectacular ones. Not only have we come a long way from the old plastic model ship in a tank days, but even from a few short years ago when we were nearly deluged by CG water in The Perfect Storm. We have Industrial Light & Magic and Scanline to thank for the latest advancements. Both are at the forefront of creating cutting-edge fluid simulation systems.

Going with the Flowline
Scanline is a Munich-based visual effects company that has formulated fluid simulation software called Flowline. Together with London-based vfx house, MPC (The Moving Picture Co.), which licensed and integrated Flowline adeptly into its pipeline, they collaborated on Poseidon.

Stephan Trojansky, Scanline’s head of R&D, points out the limitations that these techniques have always had. “First, the simulation detail didn’t match real world properties, especially on large scale scenes preventing correct fine scale motion. Second, the rendering techniques didn’t provide the correct detail and had been rather cheats with volumetric particles or polygons than real physically correct refractive droplets, sheets and volumes of water. Third, and sometimes even more important, there has always been the struggle about how to control dynamic simulations so that they fit the directors need but still keep the natural behavior and look of water and fire.”

According to Poseidon’s overall visual effects supervisor, Boyd Shermis, the creative and technical challenges they faced forced them to make advancements over then-existing fluid emulation technology. “The semantics of emulation vs. simulation notwithstanding, we needed to be able to do things with water or fire, oil, smoke and dust on a scale that hadn’t been approached before. And there were no proven pipelines to make it run up and render in the way we were expecting it to work. For their part, ILM was being asked to simulate full, volumetric (3D) water on a scale that allowed a 1,200-foot ship to interact with it. [In other words], the ship (with a record number of polygons) had to be hit by, then rollover down into, through and up out of the water — and then roll back down into it again. And that was just in one scene.

Hi-res simulations of Multiple Phase Flows within Flowline created the details in this water from Poseidon. The swimming and burning oil interacted with the water and then reacted to the air turbulence created by the waves. Courtesy of MPC.

“I needed to have the bubbles and/or foam and/or spray to be truly borne from the volume, not as an added element on top of the volume. I needed to see the true interaction of the ship displacing and motivating motion within the volume of water. And to scatter light within the volume and the bubbles/foam/spray. These are all things that might have been done before, but at nowhere near the scale or complexity that we required, both in terms of area coverage and in number of shots. So ILM was asked to rewrite their water code on our behalf to accommodate all these things. [Then] there was the issue of time. Running these kinds of simulations have been notoriously compute intensive and were literally taking weeks to run up. ILM, in association with Stanford’s computer science department, managed to break the frames down into smaller bites, or tiles, in order to ‘parallel-ize’ the computing effort over several processors (between 8-16) to speed up the process of simulation run ups. This was a tremendous leap forward for them.

“In terms of the MPC and Scanline efforts, there were a couple of areas that forced them to advance the Flowline software. Flowline is a very unique and capable piece of liquid simulation software. Scanline has been using it well for several years, obviously. And while it has had the ability to do water, fire, smoke or other viscous fluids, it has never been called upon to do all of those at once, in a single simulation, all confined in a very complex, hard surface environment. And it has never been asked to scale up to 4K for run up and rendering. And it has never been asked to do it in a massive Linux render farm. When MPC researched and ultimately licensed Flowline, they realized that it was mental ray-dependent and MPC themselves had to switch their entire rendering pipeline to mental images’ mental ray to accommodate the use of Flowline. Having now stretched the capabilities of Flowline as we have, I think that, within the industry in general, there will be a greater inclination toward using viable 3D solutions where once only practical, filmed elements would have been considered. 3D water and fire of this caliber will become the expected norm in the vfx toolset.”