Issue link: https://digital.copcomm.com/i/77744
n n n n VFX•CG Films complete with a vicious storm that threatens the characters. "We had lots of things to deal with in this film, the ocean being one of the biggest," says Kirk Garfield, CG supervisor. "In Ice Age 4, our characters spend a lot of time in or on the ocean surface. It was crucial that we develop practical solutions to several water-related challenges." In addition, the film (directed by Steve Marti- no and Mike Thurmeier) required a great deal of destruction, as one can imagine, which became the third major technical hurdle. in the SIGGRAPH 2004 Course notes. With that as a starting point, effects TDs recompiled and ported the information over to Autodesk's Maya so the data could be shared among the other groups. "For workflow reasons, it was important for us to select a real-time deformer method as opposed to simulations," says Garfield of the solution. That's because the director, art director, and then animation department had to be able to visualize what the final meshes would look like before there were any—the surface around the characters," says Adams. These final localized meshes would also be used by the effects group to set up splashes, ripples, froth, and so forth. All the ocean water was rendered using de- formed polygonal meshes. According to Gar- field, it became obvious early in the process that the resolution required for the polygonal meshes would be memory-intensive. "To deal with this, we developed a camera-dependent approach for building and subdividing the ocean meshes to the camera frustum," he ex- A good deal of the movie takes place on the ocean, so it was crucial that the previs and camera departments be able to visualize the water surface in real time. Water Work Because the ocean was such an extensive en- vironment in the film, the crew had to devise a solution to enable the previs and camera/ staging departments to visualize the surfaces in real time. Once that was done, the team had to develop a tool set and pipeline that would enable the virtual ocean to be shared by others within various departments and using differ- ent software. Lastly, the group had to devise a solution that was producible within established memory footprints and time constraints. While the earlier Ice Age films had their fill of water, some more so than others, that technology wasn't practical for the task here. "With more than 500 shots requiring ocean surfaces, we needed a more robust tool set and pipeline," says Garfield. group settled on a Side Effects Software Houdini-based solution—more specifically, Drew Whitehouse's open-source statistical wave generator, also known as Houdini Ocean Toolkit, a package of algorithms based on Jerry Tessendorf 's deep ocean waves described After exploring a number of options, the 62 June/July 2012 look would be established in previs and locked for the rest of the pipeline. "The procedural nature of this system gave us unlimited variation in movement and shape, allowing us to scout the surface for the perfect waves to shoot the action," says Mark Adams, effects TD. "We were able to dial detail in and out by layering many ocean deformers to create the biggest waves down to the finest surface ripple. We then used the deformer to drive the animation of all the ves- sels and characters on the surface of the water." To store the approved settings for each shot, a Python-based preset management system was established, accessible from both Maya and Houdini. While the animation depart- ment adjusted the character or vessel to the approved surface in Maya, the effects depart- ment continued to refine the final meshes. Once the final-resolution ocean mesh was ap- proved, the animators incorporated that into their final animation. "Sending them the entire mesh was mem- ory-prohibitive, so we developed a system to create patches from the high-resolution ocean plains. Once the main surface was approved, the effects team would extend and close the surface, enabling them to take advantage of scatter absorption and physically correct re- fractions from the studio's proprietary ren- derer, CGI Studio. Generating Atmosphere Of course, no perilous high-seas drama would be complete without supporting atmospheric effects. For the film, the crew generated a vast amount of weather and destruction VFX: a waterspout, cloud vortices, large-scale splashes of vaporized water; and on land: rolling dust clouds and other dust effects. In all, Ice Age 4 contains 413 voxel effects. The key to producing all these effects within a reasonable render window was through the use of voxel deformers that enabled the crew to add detail, modify the simulations, and cull the data. "We needed to improve the capabili- ties of our renderer [in previous productions] so we could intersect multiple voxel volumes composed of different media," explains An- drew Schneider, senior effects TD.