A linearly convergent iterative algorithm that approximates therank-1 convex envelope $f^{rc}$
of a given function $f:\mathbb{R}^{n\times m} \to \mathbb{R}$
, i.e. the largest function below f which is convex along all rank-1 lines, isestablished. The proposed algorithm is a modified version of an approximationscheme due to Dolzmann and Walkington.