Atlas
1995

Level sets

How can one boundary become two, without anyone deciding where to cut?

Primary source R. Malladi, J. A. Sethian and B. C. Vemuri, “Shape modeling with front propagation: a level set approach,” IEEE Transactions on Pattern Analysis and Machine Intelligence, vol. 17, no. 2, pp. 158–175, 1995. doi:10.1109/34.368173

Left: a function φ drawn as a surface over the image; its zero level set (gold) is the boundary. Right: the same boundary on the image. One contour around two objects shrinks, pinches, and becomes two. Started inside a cell instead, the front flows around the dark nucleus and closes behind it. Nothing in the program decides where to cut.

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