A technical sketch presented in the Feature Creatures session at SIGGRAPH 2004

The Tar Monster
Creating a Character with Fluid Simulation

Mark Wiebe
Frantic Films
mwiebe @ franticfilms.com
Ben Houston
Exocortex Technologies, Inc
ben @ exocortex.org

General Website Navigation:
Ben Houston's Homepage    The Project Gallery

Other SIGGRAPH / ACM TOG sketches & publications:
Hierarchical RLE Level Set: A Compact and Versatile Deformable Surface Representation (ACM TOG January 2006)
Visual Simulation of Wispy Smoke - A particle-based and multi-resolution approach (SIGGRAPH 2005)
Gigantic Deformable Surfaces - a novel level set data structure combining DT-Grid and RLE features (SIGGRAPH 2005)
RLE Sparse Level Sets - a fast and scalable implicit surface representation (SIGGRAPH 2004)
Modeling Complex Occlusions in Fluid Simulations - a unified level set-based approach (SIGGRAPH 2003)
Clara.io: Online 3D editor (another of my projects) ThreeKit: Online 3D Product Configurators (yet, another of my projects)

Images 2004 Warner Bros.


Creating the Tar Monster in Scooby Doo 2 presented a unique challenge, because the desired effect of a continually flowing textured character with expressive features had never been done before. Starting from a fluid simulator as in [Enright et al. 2002], we developed the liquid skin technique which applies a fluid layer over an animated character. In addition, the facial animation was preserved by using localized morphing, whereby a specified portion of the simulation is made to match the Tar Monster geometry. The result is a character from whom fluid constantly emanates, with texture sliding down its body and fluid splashing during vigorous arm gestures.  Similar previous work includes [Sumner et al. 2003], where the �TX� character is gradually liquefied. Our method, while producing a comparable result in that texture is applied to fluid flow on a character, uses quantities defined over the volume rather than particles for control and texture coordinates.

In addition to using the liquid skin and localized morphing techniques described in this short sketch, we also made use of level set morphing (originally developed by David Breen and Ross Whitaker) in two shots.  More information about how the high resolution level set morphing was achieved can be found in the forthcoming ACM Transactions on Graphics paper entitled "Hierarchical RLE Level Set: A Versatile and Compact Level Set Representation."

What people are saying about the Tar Monster special effect:

"Frantic did an amazing job on very short order on the Tar Monster... it turned into the biggest and most involved monster of them all."
    - Raja Gosnell - Director, Scooby Doo 2: Monsters Unleashed.

"We did some tests with other companies and what [Frantic Films] did in terms of their flow dynamics.  From the get-go, Frantic was so much more impressive than anybody else.  They specifically had such a great grasp on taking this character and making him as real as can be in the live action world."
    - Richard Suckle - Producer, Scooby Doo 2: Monsters Unleashed.

"The National Research Council of Canada has named [Frantic Films] one of Canada's Innovation Leaders. [...] the honor was bestowed largely because of new technology developed by Frantic for its FX work on the Warner Bros. hit sequel Scooby-Doo 2: Monsters Unleashed. The fluid simulation technology [...] was developed to create the Tar Monster character by Frantic's R&D team, including Ben Houston, Mark Wiebe and Christopher Batty.
 - "Frenzy of success for Frantic Films", Playback Magazine, May 24 2004.

"Based on [the fluid simulator's] strength, Frantic was able to win the Tar Monster contract even while competing against the major U.S.-based studio that was animating other characters in Scooby Doo II."
 - "Animation Software Creates a Splash", National Research Council of Canada.

Related external sites:


Wiebe, M. & B. Houston. (2004)  "The Tar Monster: Creating a Character with Fluid Simulation." Proceedings of the SIGGRAPH 2004 Conference on Sketches & Applications. ACM Press. [PDF]  (Supplementary Materials [PDF])


   author = {Mark Wiebe and Ben Houston},
   title = {The Tar Monster: Creating a Character with Fluid Simulation},
   booktitle = {Proceedings of the SIGGRAPH 2004 Conference on
       Sketches \& Applications},
   year = {2004},
   location = {Los Angeles, California},
   publisher = {ACM Press},

This research was supported in part by NRC IRAP Grant #482564.