Eitan Grinspun

One example of an Eitan Postdoctoral Fellow working with Prof. Denis Zorin
Media Research Lab
Courant Institute of Mathematical Sciences
New York University
Received Ph.D. in Computer Science, June 2003, Caltech.
Alumnus of the Multi-Res Modeling Group, Caltech.
Now at the Media Research Lab, Courant Institute of Mathematical Sciences.

Curriculum Vitae: download PDF

Research Statement: download PDF

Contact Info:
Media Research Lab
Courant Institute
New York University
719 Broadway, 12th Floor
New York, New York 10012
Fax: 212.995.4122
Vox: 212.998.3510
Net: eitan [@] cat.nyu.edu

 


Publications

Discrete Shells simulation of rolled, creased, pinned poster. Discrete Shells (Eitan Grinspun, Anil Hirani, Mathieu Desbrun and Peter Schröder), Symposium on Computer Animation 2003. Abstract: In this paper we introduce a discrete shell model describing the behavior of thin flexible structures, such as hats, leaves, and aluminum cans, which are characterized by a curved undeformed configuration. Previously such models required complex continuum mechanics formulations and correspondingly complex algorithms. We show that a simple shell model can be derived geometrically for triangle meshes and implemented quickly by modifying a standard cloth simulator. Our technique convincingly simulates a variety of curved objects with materials ranging from paper to metal, as we demonstrate with several examples including a comparison of a real and simulated falling hat.


Frames from a Navier-Stokes solver running in real time on the GeForce FX Sparse Matrix Solvers on the GPU: Conjugate Gradients and Multigrid (Jeff Bolz, Ian Farmer, Eitan Grinspun and Peter Schröder), to appear SIGGRAPH 2003. Abstract: Many computer graphics applications require high-intensity numerical simulation. We show that such computations can be performed efficiently on the GPU, which we regard as a full function streaming processor with high floating-point performance. We implemented two basic, broadly useful, computational kernels: a sparse matrix conjugate gradient solver and a regular-grid multigrid solver. Realtime applications ranging from mesh smoothing and parameterization to fluid solvers and solid mechanics can greatly benefit from these, evidence our example applications of geometric flow and fluid simulation running on NVIDIA's GeForce FX using geometric flow (cube smoothing movie, 3D photography scan denoising movie) and fluid simulation (particle advection movie) as application examples.


Pillows and balloons modeled with CHARMS. CHARMS: A Simple Framework for Adaptive Simulation (Eitan Grinspun, Petr Krysl and Peter Schröder), ACM TOG, 2002 / Proceedings of SIGGRAPH 2002. Abstract: Finite element solvers are a basic component of simulation applications; they are common in computer graphics, engineering, and medical simulations. Although adaptive solvers can be of great value in reducing the often high computational cost of simulations they are not employed broadly. Indeed, building adaptive solvers can be a daunting task especially for 3D finite elements. In this paper we are introducing a new approach to produce conforming, hierarchical, adaptive refinement methods (CHARMS). The basic principle of our approach is to refine basis functions, not elements. This removes a number of implementation headaches associated with other approaches and is a general technique independent of domain dimension (here 2D and 3D), element type (eg, triangle, quad, tetrahedron, hexahedron), and basis function order (piecewise linear, higher order B-splines, Loop subdivision, etc.). The (un-)refinement algorithms are simple and require little in terms of data structure support. We demonstrate the versatility of our new approach through 2D and 3D examples, including medical applications and thin-shell animations.


Adapted FEM model of brain tissue. Natural Hierarchical Refinement for Finite Element Methods (Petr Krysl, Eitan Grinspun, and Peter Schröder), International Journal for Numerical Methods in Engineering, 2003. Abstract: Current formulations of adaptive finite element mesh refinement seem simple enough, but their implementations prove to be a formidable task. We offer an alternative approach called CHARMS: Conforming Hierarchical Adaptive Refinement Methods. Our method yields equivalent adapted approximation spaces wherever the traditional mesh refinement is applicable, but proves to be significantly simpler to implement. At the same time it is much more powerful in that it is general (no special tricks are required for different types of finite elements), and applicable for some newer approximations where traditional mesh refinement concepts are not of much help, for instance on subdivision surfaces.


Control mesh of a bent can, and self-interference
regions on the limit surface resolved with increasing precision. Normal Bounds for Subdivision-Surface Interference Detection (Eitan Grinspun and Peter Schröder), Proceedings of IEEE Scientific Visualization, 2001. Abstract: Interference detection is vital for simulation and animation. Our interest was born of a larger project: using the Subdivision Element Method and the thin-shell equations we produce realistic animations of crushing, crumpling, and wrinkling. In this paper we derive normal bounds for subdivision surfaces and use these to develop an efficient algorithm for collision detection with specific optimizations for self-interference. The normal bounds are also useful for CAD and rendering.


A sequence from our simulation of crushing aluminum cans. Non-Linear Mechanics and Collisions for Subdivision Surfaces (Eitan Grinspun, Fehmi Cirak, Peter Schröder, and Michael Ortiz), Technical Report, 1999. Abstract: Numerically accurate simulation of the mechanical behavior of thin flexible structures is important in application areas ranging from engineering design to animation special effects. Subdivision surfaces provide a unique opportunity to integrate geometric modeling with concurrent finite element analysis of thin flexible structures. Their mechanics are governed by the so-called thin-shell equations. We present a concise treatment of thin-shell equations including dynamic behavior, scalable material models, and the treatment of collisions (detection as well as response). The resulting energy minimization problem is non-linear and in turn able to capture effects of far more realism than linear models. We demonstrate these claims with a number of simulations which exhibit characteristic effects of real world experiments.

Copyright © 2002 Eitan Grinspun  Modified: Feb 2004