  We briefly review a fruitful approach to compute a variety of radiation
signatures of General Relativity (GR) originating from accretion disks in
strong gravity. A set of transfer functions can be pre-computed and then
employed to accelerate the ray-traycing computations, generate a series of
model spectra, and to fit the model predictions to actual data sets in X-rays.
We have been developing this method to examine spectra and light curves and to
model the expected polarimetric properties; in particular, to analyse the
properties of the "corona--disk-line" geometry with GR effects taken into
account. New impetus to this activity is emerging in the anticipation of
upcoming missions equipped with the sensitivity to polarimetric properties in
X-rays: IXPE (Imaging X-Ray Polarimetry Explorer) and eXTP (enhanced X-ray
Timing and Polarimetry mission).
