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SHAPE MATCHING IN HOUDINI
Implemented a shape matching algorithm in Houdini using VOP, based on "Meshless Deformation Based On Shape Matching" (Müller et al., 2005)
DATE
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Oct 2011
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Shape Matching in Houdini
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Implemented a shape matching algorithm in Houdini using VOP. This is based on “Meshless Deformation Based On Shape Matching” (Müller et al., 2005).

Given a set of non-connected point cloud, the algorithm fits the original geometry into it in the best way possible.

The most involved part in the algorithm is finding the square root of a symmetric matrix. It’s interesting to know that Houdini has a VOP that returns the eigenvalues of a matrix, but not their corresponding eigenvectors :( The eigenvalues and eigenvectors would have been useful in transforming the matrix into a diagonal matrix in another basis and thus making the square root easy to calculate. Used the Denman-Beaver iteration in the end instead and it seems to work pretty well.

This is just the first part – shape matching. What’s left to be done is to use this shape-matched geometry as a goal for each vertex for soft body deformations, using the unconditionally stable integration method mentioned in the paper.


 
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Skeel Lee Skeel Lee
skeel@skeelogy.com
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Senior FX TD / R&D
Digital Domain 3.0 (Previously at Sony Pictures Imageworks, MPC, Industrial Light & Magic, Double Negative)
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I am a Senior Technical Director with strong interests in both tech and art. My life evolves round VFX, photography, software engineering, tools programming and generally anything that looks / sounds cool.
I have done a variety of CG programming, including fluid sims, muscles, soft/rigid bodies, raytracing etc. These knowledge complement the visual works that I do as a TD in VFX.
I was interviewed by The Straits Times in May 2014 for my VFX work in X-Men: Days of Future Past.