  We extend the maximal unitarity method to amplitude contributions whose cuts
define multidimensional algebraic varieties. The technique is valid to all
orders and is explicitly demonstrated at three loops in gauge theories with any
number of fermions and scalars in the adjoint representation. Deca-cuts
realized by replacement of real slice integration contours by
higher-dimensional tori encircling the global poles are used to factorize the
planar triple box onto a product of trees. We apply computational algebraic
geometry and multivariate complex analysis to derive unique projectors for all
master integral coefficients and obtain compact analytic formulae in terms of
tree-level data.
