  The straightforward method of transformation optics implies that one starts
from the coordinate transformation, determines the Jacobian matrix, the fields
and material parameters of the cloak. However, the coordinate transformation
appears as an optional function: it is not necessary to know it. We offer the
solution of some sort of the inverse problem: starting from the fields in the
invisibility cloak we directly derive the permittivity and permeability tensors
of the cloaking shell. The approach can be useful for finding material
parameters for the specified electromagnetic fields in the cloaking shell
without knowing coordinate transformation.
