Paper (2009) In IEEE Transactions on Visualization and CG “Fluid Simulation with Articulated Bodies”

June 10th, 2009 Irfan Essa Posted in Greg Turk, Modeling and Animation, Nipun Kwatra No Comments »

Nipun Kwatra, Chris Wojtan, Mark Carlson, Irfan A. Essa, Peter J. Mucha, Greg Turk (2009), “Fluid Simulation with Articulated Bodies“, IEEE Transactions on Visualization and Computer Graphics, 10 Jun. 2009. IEEE computer Society Digital Library. IEEE Computer Society. [DOI | PDF (see copyright) | Video | Website]


We present an algorithm for creating realistic animations of characters that are swimming through fluids. Our approach combines dynamic simulation with data-driven kinematic motions (motion capture data) to produce realistic animation in a fluid. The interaction of the articulated body with the fluid is performed by incorporating joint constraints with rigid animation and by extending a solid/fluid coupling method to handle articulated chains. Our solver takes as input the current state of the simulation and calculates the angular and linear accelerations of the connected bodies needed to match a particular motion sequence for the articulated body. These accelerations are used to estimate the forces and torques that are then applied to each joint. Based on this approach, we demonstrate simulated swimming results for a variety of different strokes, including crawl, backstroke, breaststroke and butterfly. The ability to have articulated bodies interact with fluids also allows us to generate simulations of simple water creatures that are driven by simple controllers.


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Event: SIGGRAPH PC Meeting at GA Tech 2008

March 30th, 2008 Irfan Essa Posted in Events, Greg Turk No Comments »

ACM SIGGRAPH 2008 Paper’s Committee Meeting was held at GA Tech in Atlanta, March 29-30, under the leadership of Greg Turk. Following is a picture of all of us at work, with our sigs, as a note of thanks for Greg


Original Photo by myself, this version with sigs by Fredo Durand.

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Paper: IEEE CVPR (2006) Element-Free Elastic Models for Volume Fitting and Capture”

June 14th, 2006 Irfan Essa Posted in Greg Turk, Modeling and Animation, Papers, Research No Comments »

Element-Free Elastic Models for Volume Fitting and Capture (IEEEXplore)

Jaeil Choi Szymczak, A. Turk, G. Essa, I.
Georgia Institute of Technology
This paper appears in: Computer Vision and Pattern Recognition, 2006 IEEE Computer Society Conference on
Publication Date: 2006
Volume: 2
On page(s): 2245 – 2252
ISSN: 1063-6919
ISBN: 0-7695-2597-0
Digital Object Identifier: 10.1109/CVPR.2006.110
Posted online: 2006-10-09 11:11:24.0


We present a new method of fitting an element-free volumetric model to a sequence of deforming surfaces of a moving object. Given a sequence of visual hulls, we iteratively fit an element-free elastic model to the visual hull in order to extract the optimal pose of the captured volume. The fitting of the volumetric model is acheived by minimizing a combination of elastic potential energy, a surface distance measure, and a self-intersection penalty for each frame. A unique aspect of our work is that the model is mesh free – since the model is represented as a point cloud, it is easy to construct, manipulate and update the model as needed. Additionally, linear elasicity with rotation compensation makes it possible to handle local deformations and large rotations of body parts much more efficiently than other volume fitting approaches. Our experimental results for volume fitting and capture in a multi-view camera setting demonstrate the robustness of element-free elastic models against noise and self-occlusions.

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Papers: ACM SIGGRAPH (2003) “Graphcut textures”

July 25th, 2003 Irfan Essa Posted in Aaron Bobick, ACM SIGGRAPH, Arno Schödl, Computational Photography and Video, Greg Turk, Papers, Vivek Kwatra No Comments »

Vivek Kwatra, Arno Schödl, Irfan Essa, Greg Turk, Aaron Bobick (2003), “Graphcut textures: image and video synthesis using graph cuts” In ACM Transactions on Graphics (TOG), Volume 22 , Issue 3, Proceedings of ACM SIGGRAPH 2003, Pages: 277 – 286, July 2003, ISSN:0730-0301. (DOI|Paper| SIGGRAPH Video (160 MB, 50 MB) | Video Results 87 MB | Project Site)


In this paper we introduce a new algorithm for image and video texture synthesis. In our approach, patch regions from a sample image or video are transformed and copied to the output and then stitched together along optimal seams to generate a new (and typically larger) output. In contrast to other techniques, the size of the GC-TOCpatch is not chosen a-priori, but instead a graph cut technique is used to determine the optimal patch region for any given offset between the input and output texture. Unlike dynamic programming, our graph cut technique for seam optimization is applicable in any dimension. We specifically explore it in 2D and 3D to perform video texture synthesis in addition to regular image synthesis. We present approximative offset search techniques that work well in conjunction with the presented patch size optimization. We show results for synthesizing regular, random, and natural images and videos. We also demonstrate how this method can be used to interactively merge different images to generate new scenes.

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