Tom Kluyskens developed two major effects in the movie: the spaghetti twister, and the Jello-O palace dynamics.

The spaghetti twister

(click for full res)

The spaghetti twister is procedurally generated and animated in Houdini. The sheer amount of twister shots, and the complexity of the twister object did not allow for hand animation, except for the central twister spine. To create the shape of the twister, a 2D SPH particle sim was extruded into curves, thus creating a dense bundle of non-intersecting spaghetti strands. Various twisting operators further shaped the bundle into a interesting twister funnel shape, which is then deformed along a twister spine. To simplify the animation of this complex object, a customized 2D to 3D mapping of the strands was developed, so that coordinates, noises and other deformations could be applied in both a 2D and 3D space. Actual twisting of the twister is done in 2D. The result is compelling twisting motion while avoiding intersection of individual strands, or over-stretching of strands, while individual strands slide over eachother. For the spaghetti strands, a stable UV space was engineered. Further work was done on stable meatball insertion and ejection, and a meatball ballistics system that allowed the directors to choreograph exact trajectory and impact point and timing of the ejecting meatballs, while keeping full procedurality.

The clouds were rendered using Imageworks’ in-house volume renderer Svea, which is fully integrated in Houdini. For the twister storm cloud, a set of concentric patches rotates around the core, their speed tapering off further away from the center. The patches carry a multitude of noise and deformation attributes that get passed on to Svea, where the patches get extruded and rendered volumetrically.

The Jell-O palace

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For the Jell-O palace sequence, a custom Houdini oscillator (the Rippler) was written based on slow-motion video footage of Jell-O in motion. The Rippler is used in combination with ‘hit points’. Hit points are recorded in space and time when a object or character touches the Jell-O surface. Together, hit points and the Rippler produce ripples along 3 axes of motion. The operator is multithreaded for interactive performance on the artists’ 8 core machines. Stacking or compositing of ripples is possible for combining frequencies and adding ripples from several sources. Various noise and decay functions create a realistic look and feel. No simming or integration is required — once the hit points are recorded, the artist can preview the ripples without preroll.

trailer (look for the Jell-O palace at 1:48)

The same Rippler is used for water ripples created by falling food, or more ordinary water-object interactions. The speed of the Rippler is such that dense clouds of hit points can be used to obtain complex rippling patterns usually reserved to sim and/or map-based systems like iwave.

Tom Kluyskens,
2009