Wave effects.(Sony Pictures Imageworks' Surf's Up )

At the onset of development, the Surf's Up effects team was given two main directives in regard to the water and wave effects: Make it look 80 percent real, and make the entire process capable of producing 20 minutes of final surfing footage as efficiently as possible.

For anyone who has worked on a large-scale project such as this, it will come as no surprise that the latter of those goals was the one that took the most work. A couple of months were required to hammer out the basic approach and produce a test that, while crude in comparison to the end product, more than adequately proved the overall technical strategies. It then took well over a year to iron out the specifics and craft a production pipeline that spanned five departments: character rigging, layout, animation, effects, and lighting.

In a collaborative effort between the effects and character rigging departments, a wave rig was developed in Autodesk's Maya that provided the motion of the surfing waves (see "Radical, Dude," pg. 12). The rig deformed a rectangular patch so that any lateral cross section of the patch could be animated through the evolution of a two-dimensional wave shape, front flat water, to tubing, through collapse, and back to flat again. By offsetting in time the animation of neighboring cross sections of the wave patch, the motion of a tubing wave could be achieved.

The waves were animated in this way entirely by hand without procedural mechanisms and with a great deal of time spent getting the motion to appear to generally obey a narrow subset of real-world characteristics, such as forward velocity, lateral break speed, a lip that fell at a speed close to gravity, plausible volume preservation, and corresponding surface stretching. For composition and timing purposes, the ability to previsualize dominant wave and surfing features, such as the white-water explosion of the crashing wave and the wake from a surfboard, was incorporated into the rig as well.

While the function of the wave rig was to provide the gross animation of the surfing waves, it was not designed to provide the small, higher-frequency waves of the water surface. Inspired in part by Tessendorf's work on simulating ocean water, we developed a Side Effects Houdini- and Pixar RenderMan-based system to simulate open ocean waves for the overall displaced water surface. The system employed "wave trains," simply defined as the sum of continuous wave patterns of varying period, amplitude, direction, and speed.

By creating sets of Gerstner-style wave trains whose speeds, by default, were physically based but whose frequency ranges and angles of propagation were hand-tailored, we chose several water surface "styles." These ranged from almost dead calm to stormy and chaotic. The frequencies of the wave trains were segregated into three ranges: low, medium, and high, each with individual control over amplitude, cuspiness, and speed. Provisions were made for general noise-based and specific hand-tailored control of areas of amplitude reduction of the wave trains for a varied and natural look of the ocean surface. The peaks of waves could be determined and isolated in the shader to create areas of aerated water or to be used as the source of emission for particle effects. Data, output from the simulation system, describing the frequency ranges and propagation angles and speeds of the wave trains was input into the water displacement shader for rendering.

Ambient foam--foam created from crashing waves, splashes, surfboard wakes, and shore break--all were critical components of the look of the Surf's Up water. From the start, it was important to create methods for general and specific foam placement, erasure, dissolution, and animation. Used not only to create a more realistic look, different foam patterns and formations were employed to distinguish wave styles and locations from one another.