Christopher Batty

Assistant Professor
Ph.D. UBC '10, BCSc. Manitoba '04
Scientific Computation Group and Computer Graphics Lab
David R. Cheriton School of Computer Science, University of Waterloo

Office: 3605 Davis Centre (DC3605)
Brief Bio
Google Scholar

Join the Computational Motion Group:
I am looking for highly motivated and hard-working grad students at the Master's and PhD level. More information here.
I am also looking to hire a postdoc, so if you have a strong track record in simulation/animation, please get in touch by email!
Recent news:


milk crown splash milk crown splash colliding drops under surface tension sub-grid solid fluid coupling on grids

About me and my research:
I do research in the area of Physics-Based Animation, which lies right at the intersection of computer graphics and computational physics. I lead the Computational Motion Group here at Waterloo, and am affiliated with both the Computer Graphics Lab and the Scientific Computation Group. The majority of my work focuses on methods for simulating liquids and gases, but I am broadly interested in applying physical simulation as a fundamental tool for generating, controlling, and predicting motion of all kinds. I seek to design algorithms that are supported by sound physical, mathematical, and geometric principles, yet are readily amenable to efficient and robust practical implementation.

As illustrated in the clips above, I have developed methods for...
  • interactions between dynamic objects and fluids
  • animating and representing thin splashes and droplets
  • viscous liquids that coil and fold when poured (honey, molasses, etc.)
  • surface tension-driven phenomena, bubbles, and foams
  • evolving multimaterial flows and geometries
Applications in the visual effects industry motivate much of my research. I am currently collaborating with Side Effects Software (makers of Houdini), and have previously worked with folks at (now-defunct) Frantic Films VFX, New Zealand's Weta Digital (of Avatar and Lord of the Rings fame), and Exocortex Technologies (makers of, the free online 3D editor). While at Frantic Films, I worked on the movies Superman Returns, Scooby Doo 2: Monsters Unleashed, and Wes Craven's Cursed. Aspects of my research have been incorporated into commercial fluid animation software by Side Effects Software (Houdini), AutoDesk (Maya/Bifrost), Exocortex Technologies, and Navié (EFFEX), and as a result have contributed to dozens of movies from major studios.

I created and continue to manage the Physics-Based Animation blog, which catalogues papers, people, and software in this area.

I have collected links to a few pieces of advice for students that you may find useful.

A cell-centred finite volume method for the Poisson problem on non-graded quadtrees with second order accurate gradients
C. Batty. In submission, major revisions.
The first cell-centred finite volume method for the variable-coefficient Poisson problem on general quadtree grids with no grading restrictions whatsoever between neighbouring cells that provides second order accuracy in both the solution variable and its gradients.
[Revised PDF]
Surface-Only Liquids
F. Da, D. Hahn, C. Batty, C. Wojtan, & E. Grinspun. ACM SIGGRAPH 2016 (Transactions on Graphics).
By building on boundary element techniques, we are able to simulate surface-tension dominated liquid effects, such as droplet collisions, fluid chains, and crown splashes, using velocity data defined only on a triangulated surface mesh.
[Project] [PDF] [Video] [YouTube] [Journal]
Preserving Geometry and Topology for Fluid Flows with Thin Obstacles and Narrow Gaps
V. Azevedo, C. Batty, & M. Oliveira. ACM SIGGRAPH 2016 (Transactions on Graphics).
We describe techniques to improve the treatment of fluid flows around arbitrarily thin solids and thin gaps in regular grid fluid simulations, including a topology-aware graph-based pressure projection for sub-grid flows and a conforming velocity interpolant to improve particle trajectories in polyhedral cut cells.
[PDF] [Project] [Journal] [YouTube]
A Practical Method for High-Resolution Embedded Liquid Surfaces
R. Goldade, C. Batty, & C. Wojtan. Eurographics 2016 (Computer Graphics Forum).
We describe a trio of practical and efficient techniques that drastically improve the simulation quality achieved when using narrow-band high-resolution level set surfaces embedded within inexpensive low-resolution fluid simulations.
[Project] [PDF] [Video] [YouTube] [Journal]
Continuum Foam: A Material Point Method for Shear-Dependent Flows
Y. Yue, B. Smith, C. Batty, C. Zheng, & E. Grinspun. ACM Transactions on Graphics, 34(5) 2015 (presented at SIGGRAPH Asia 2015).
A material point method for animating the behavior of dense foams, such as whip cream or shaving cream, using a continuum-based non-Newtonian fluid model that supports shear thinning effects. Our model also supports shear thickening, which enables the animation of unusual materials like silly putty or "oobleck".
[PDF] [Project] [YouTube] [Journal]
Double Bubbles Sans Toil and Trouble: Discrete Circulation-Preserving Vortex Sheets for Soap Films and Foams
F. Da, C. Batty, C. Wojtan, & E. Grinspun. ACM SIGGRAPH 2015 (Transactions on Graphics 34(4), 2015).
A "surface-only" method for simulating the complex dynamics of soap bubbles and foams, using a vortex sheet method with surface tension forces on a non-manifold triangle mesh.
[PDF] [Project] [Video] [YouTube] [Journal]
Multimaterial Mesh-Based Surface Tracking
F. Da, C. Batty, & E. Grinspun. ACM SIGGRAPH 2014 (Transactions on Graphics, 33(4), 2014).
The first collision-safe triangle mesh-based surface tracking method for evolving multimaterial geometries, including strategies for multimaterial topological changes: merging, splitting, and the foam-type operations known as T1 and T2 processes.
[PDF - High] [PDF - Low] [Project] [Video] [Code] [Journal]
Discrete Viscous Sheets
C. Batty, A. Uribe, B. Audoly, & E. Grinspun. ACM SIGGRAPH 2012 (Transactions on Graphics, 31(4), 2012).
A method for animating thin sheets of highly viscous liquid, drawing on and extending techniques from the simulation of thin shells and cloth.
[PDF] [Project] [Video] [Journal]
A Simple Finite Volume Method for Adaptive Viscous Liquids
C. Batty & B. Houston. ACM SIGGRAPH/Eurographics Symposium on Computer Animation 2011.
An Eulerian approach to achieve higher detail animations of high viscosity liquid behaviour (buckling, coiling, etc.) on structured tetrahedral meshes.
[PDF] [Journal] [Video]

Computational Physics in Film
R. Bridson & C. Batty. Science 330(6012): 1756-1757.
A perspective piece on the increasingly common use of physical simulation in visual effects for film, along with discussion of some major challenges that remain.
[PDF] [Journal]

Simulating Viscous Incompressible Fluids with Embedded Boundary Finite Difference Methods
C. Batty. PhD Thesis, University of British Columbia.
[PDF] [Thesis Repository]

Matching Fluid Simulation Elements to Surface Geometry and Topology
T. Brochu, C. Batty, & R. Bridson. ACM SIGGRAPH 2010 (Transactions on Graphics, 29(4), 2010).
By adding simulation degrees of freedom exactly where they provide the most benefit, and using a triangle mesh-based surface representation, we show how to achieve much greater detail in liquid animations.
[PDF] [Project] [Journal]

Tetrahedral Embedded Boundary Methods for Accurate and Flexible Adaptive Fluids
C. Batty, S. Xenos, & B. Houston. Eurographics 2010 (Computer Graphics Forum, 29(2), 2010).
This paper demonstrates that combining embedded boundary methods with tetrahedra-based fluid simulation enables spatially adaptive liquid simulation with more accurate enforcement of air and solid boundary conditions.
[PDF] [Project] [Journal]

Accurate Viscous Free Surfaces for Buckling, Coiling and Rotating Liquids
C. Batty & R. Bridson. ACM SIGGRAPH/Eurographics Symposium on Computer Animation 2008.
A simple method to enforce physically correct forces at the surface of viscous liquids, such as honey or syrup, which in turn lets us reproduce previously very difficult effects like buckling, coiling, and rotational motion.
[PDF] [Project] [Journal]

A Fast Variational Framework for Accurate Solid-Fluid Coupling
C. Batty, F. Bertails, & R. Bridson. ACM SIGGRAPH 2007 (Transactions on Graphics, 26(3), 2007).
An optimization-based framework for accurately incorporating irregularly shaped rigid objects into standard grid-based fluid simulations, eliminating spurious "stairstep" artifacts and leakage that plagued previous methods.
[PDF] [Project] [Journal]

Hierarchical RLE Level Set: A Compact and Versatile Deformable Surface Representation
B. Houston, M. Nielsen, C. Batty, O. Nilsson, & K. Museth. ACM Transactions on Graphics, 25(1), 2006.
A compressed representation of level set implicit surfaces that avoids storing and processing irrelevant data far from the surface itself, allowing more efficient treatment of operations like morphing and liquid surface tracking.
[PDF] [Project] [Journal]

Short Papers & SIGGRAPH Talks/Sketches:
Regional Time Stepping for SPH
P. Goswami & C. Batty. Eurographics Short Papers, 2014.
A method to accelerate weakly compressible SPH simulations by exploiting spatially varying, asynchronous time integration.
[PDF] [Journal]

Visual Simulation of Wispy Smoke
C. Batty & B. Houston. ACM SIGGRAPH Sketches, 2005.
A description of the smoke simulation techniques used on Wes Craven's werewolf movie Cursed.
[PDF] [Project] [Journal]

Gigantic Deformable Surfaces
B. Houston, M. Nielsen, C. Batty, O. Nilsson, & K. Museth. ACM SIGGRAPH Sketches, 2005.
A preview of the HRLE level set described more fully in the TOG paper above.
[PDF] [Project] [Journal]

RLE Sparse Level Sets
B. Houston, M. Wiebe, & C. Batty. ACM SIGGRAPH Sketches, 2004.
A compressed level set representation that was the precursor to the eventual HRLE level set above.
[PDF] [Project] [Journal]

Student Supervision:

I work with a team of skilled and dedicated graduate students who collectively comprise the Computational Motion Group.

Current: Past:

CS370 Numerical Computation - Spring 2016
CS888 Advanced Topics in Computer Graphics: Physics-Based Animation - Winter 2016
CS475 Computational Linear Algebra - Spring 2015
CS370 Numerical Computation - Fall 2014
CS888 Advanced Topics in Computer Graphics: Physics-Based Animation - Winter 2014

Old Slides on Fluids: A friendly introduction to Eulerian fluid animation for computer graphics.

Code and Data:

Below you'll find miscellaneous sample code and data from some of my projects; in other cases you can find the code for a given publication on its associated project page (linked above). Buyer beware, of course, but I'd love to hear from you if you do put any of it to use!

Los Topos
The code for our multimaterial mesh-based surface tracking library, as described in our appropriately-named SIGGRAPH 2014 paper "Multimaterial Mesh-Based Surface Tracking". It generalizes and extends the original El Topo framework of Tyson Brochu and Robert Bridson to the case of multiple materials, and includes an improved merging strategy that is effective even in the standard two-material case.
Non-manifold Simplicial Complex Mesh Library
This is my own implementation of a non-manifold simplicial complex-based mesh library, including arbitrary data associated to vertices, edges, triangles and tetrahedra. It's essentially my spin on the data structure outlined in "Building Your Own DEC at Home" with an API similar to "Design, Implementation, and Evaluation of the Surface_mesh Data Structure". The main goal is to allow non-manifold geometry and mixed dimensional components (tets, tris, segments), while being relatively simple to manipulate. It's a work in progress and not currently being maintained.
[GitHub link]
3D Liquid Simulator code
A minimal grid-based 3D liquid simulator and OpenGL viewer, using semi-Lagrangian advection, volumetric particles for the liquid, ghost fluid free surface conditions, and support for irregular solid boundaries using the variational/finite-volume approach from our SIG'07 paper. The only dependencies should be the GLUT library, so it's hopefully easy to set up and experiment with. Here's a sample clip. Update: I also added another version with our variational viscosity technique implemented in 3D.
[Inviscid code, on GitHub] [With viscosity, on GitHub]
2D Variational Viscosity code
Sample code illustrating how to use our variational viscosity discretization to support rotation and buckling and variable viscosity within the liquid solver below. (The link for the comparable 3D code is above.)
[Github link]
2D Variational Pressure Projection code
Sample codes illustrating how to use our variational pressure projection to support static irregular geometry within a very simple 2D "stable fluids" style fluid solver.
Air - Single phase fluid solver with static obstacles.
Liquid - Free surface liquid solver with static obstacles. This code combines our irregular solid boundary discretization with the 2nd order free surface pressure boundary condition of Enright et al. 2003.
SDFGen: Signed Distance Field Generator for triangle meshes
A simple command-line utility to construct a signed distance field from a triangle mesh, which is often useful for physics-based animation, such as in processing collisions for rigid objects.
[Github link]
Watertight Stanford bunny
I ran into some problems due to the holes in the bunny, and since I couldn't find a watertight version online, I made one myself (for non-commercial use, of course). It's also in OBJ format, rather than the original PLY. Thanks to the Stanford 3D Scanning Repository for the original model.
2D Polygon Moment of Inertia Tensor Code
I couldn't find any convenient code for computing 2D inertia tensors from the vertices and edges of a simple polygon, so I adapted/specialized Michael Kallay's excellent 3D code from the Journal of Graphics Tools article Computing the Moment of Inertia of a Solid Defined by a Triangle Mesh. The article mentions how to handle 2D bodies, but the accompanying code supports only 3D objects. My code provides the corresponding 2D implementation, while retaining the speed, brevity, and clarity of the original.
Higher Order Data Extrapolation in the Normal Direction
A sample Matlab implementation of quadratic extrapolation in the normal direction of a function from a region defined by a given signed distance function into a surrounding undefined region, essentially following Ng et al. 2009, Min & Gibou 2007, and Aslam 2003. This can be useful for extrapolating known velocities from a fluid region into a solid region, such as in the Ghost Fluid Method, for example. [Note: I haven't actually rigourously verified the target order of convergence is achieved.]

For two years following my PhD (2011-2013) I was a postdoc in the Computer Science Department at the Columbia University in New York City, supported by an NSERC Banting Fellowship. My advisor was Dr. Eitan Grinspun.
My PhD is from the Computer Science Department at the University of British Columbia in Vancouver, BC. I worked under the supervision of Dr. Robert Bridson, beginning in 2005 and defending in 2010. During my degree I consulted for Ottawa-based Exocortex Technologies, and interned at Weta Digital in New Zealand, and Intel's Applications Research Lab in Santa Clara, California.
Prior to my academic career, I spent 2004-2005 working at former Winnipeg-based visual effects studio, Frantic Films, where I was a Software Engineer in Research and Development. My job was to develop physics tools for artists based on recent academic research, including smoke, water, and rigid and deformable bodies. These tools were used on various films, including Superman Returns, Scooby-Doo 2: Monsters Unleashed, and Cursed. (Much of the software division is now at Thinkbox Software.)
I'm a graduate of the Computer Science Honours Co-op program at the University of Manitoba, having completed my Bachelor of Computer Science degree in the fall of 2003. In addition to Frantic Films, I also interned at OTI (original developers of Eclipse, now a subset of IBM) and Protegra, Inc.

Past and Current Collaborators:

  Basile Audoly, Vinicius C. Azevedo, Florence Bertails-Descoubes, Robert Bridson, Tyson Brochu, Fang Da, Ryan Goldade, Prashant Goswami, Eitan Grinspun, David Hahn, Ben Houston, Ken Museth, Michael Nielsen, Manuel Oliveira, Breannan Smith, Chris Wojtan, Yonghao Yue, Changxi Zheng

  Some stray thoughts about the problem of reconstructing tri-meshes from signed distances.