  It has recently been argued that Casimir-Lifshitz forces depend in detail on
the microphysics of a system; calculations of the Casimir force in
inhomogeneous media yield results that are cutoff-dependent. This result has
been shown to hold generally. But suppose we introduce an inhomogeneous
metamaterial into a cavity that effectively implements a simple distortion of
the coordinate system. Considered in its 'virtual space', the optical
properties of such a material are homogeneous and consequently free from the
cutoff-dependency associated with inhomogeneous media. This conclusion should
be reconciled with recent advances in our understanding of Casimir-Lifshitz
forces. We consider an example of such a system here and demonstrate that,
whilst the size of the Casimir force is modified by the inhomogeneous medium,
the force is cutoff-independent and can be stated exactly. The apparent paradox
dissolves when we recognise that an idealised metamaterial that could implement
a virtual geometry for all frequencies would be devoid of internal scattering,
and would not give rise to a cutoff-dependency in the Casimir force for that
reason.
