An energy-driven approach to linkage unfolding

@inproceedings{Cantarella2004AnEA,
  title={An energy-driven approach to linkage unfolding},
  author={Jason H. Cantarella and Erik D. Demaine and Hayley N. Iben and James F. O'Brien},
  booktitle={SCG '04},
  year={2004}
}
We present a new algorithm for unfolding planar polygonal linkages without self-intersection based on following the gradient flow of a "repulsive" energy function. This algorithm has several advantages over previous methods. (1) The output motion is represented explicitly and exactly as a piecewise-linear curve in angle space. As a consequence, an exact snapshot of the linkage at any time can be extracted from the output in strongly polynomial time (on a real RAM supporting arithmetic, radicals… 

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