A method of mesh simplification developed by Michael Garland and Paul S. Heckbert of CMU. Vertex pairs are iteratively contracted to simplify the mesh. Error values for the resulting points of a contraction are maintained using a quadric matrix. Error is computed by usuing the sum squared distance of the new point from the 3 planes that meet to form the original. Important because of its use of pair, rather than edge, contractions, allowing non-connectected regions of space to become connected.