Takeo Igarashi, Tomer Moscovich, John F. Hughes, "As-Rigid-As-Possible Shape Manipulation", ACM Transactions on Computer Graphics, Vol.24, No.3, ACM SIGGRAPH 2005, Los Angels, USA, 2005.

[The PDF is here.](http://www-ui.is.s.u-tokyo.ac.jp/~takeo/papers/rigid.pdf)