Closest Point Turbulence for Liquid Surfaces

Theodore Kim, Jerry Tessendorf, Nils Thuerey

We propose a method of increasing the apparent spatial resolution of an existing liquid simulation. Previous approaches to this “up-resing” problem have focused on increasing the turbulence of the underlying velocity field. Motivated by measurements in the free surface turbulence literature, we observe that past certain frequencies, it is sufficient to perform a wave simulation directly on the liquid surface, and construct a reduced-dimensional surface-only simulation. We sidestep the considerable problem of generating a surface parameterization by employing an embedding technique known as the Closest Point Method (CPM) that operates directly on a 3D extension field. The CPM requires 3D operators, and we show that for surface operators with no natural 3D generalization, it is possible to construct a viable operator using the inverse Abel transform. We additionally propose a fast,frozen core closest point transform, and an advection method for the extension field that reduces smearing considerably. Finally, we propose two turbulence coupling methods that seed the high resolution wave simulation in visually expected regions.

Closest Point Turbulence for Liquid Surfaces

Sci-Tech Oscars

The Oscars for Scientific and Technical Achievement were announced recently, and among them are a pair of tools for physics-based animation:

  • To Theodore KimNils ThuereyMarkus Gross and Doug James for the invention, publication and dissemination of Wavelet Turbulence software.

    This technique allowed for fast, art–directable creation of highly detailed gas simulation, making it easier for the artist to control the appearance these effects in the final image.

  • To Simon ClutterbuckJames Jacobs and Dr. Richard Dorling for the development of the Tissue Physically–Based Character Simulation Framework.

    This framework faithfully and robustly simulates the effects of anatomical structures underlying a character’s skin. The resulting dynamic and secondary motions provide a new level of realism to computer–generated creatures.

Full list and further details at the Academy awards website.

Artistic Simulation of Curly Hair

Hayley Iben, Mark Meyer, Lena Petrovic, Olivier Soares, John Anderson, Andrew Witkin

We present a novel method for stably simulating stylized curly hair that addresses artistic needs and performance demands, both found in the production of feature films. To satisfy the artistic requirement of maintaining the curl’s helical shape during motion, we propose a hair model based upon an extensible elastic rod. We introduce a novel method for stably computing a frame along the hair curve, essential for stable simulation of curly hair. Our hair model introduces a novel spring for controlling the bending of the curl and another for maintaining the helical shape during extension. We also address performance concerns often associated with handling hair-hair contact interactions by efficiently parallelizing the simulation. To do so, we present a novel algorithm for pruning both hair-hair contact pairs and hair particles. Our method is in use on a full length feature film and has proven to be robust and stable over a wide range of animated motion and on a variety of hair styles, from straight to wavy to curly.

Artistic Simulation of Curly Hair