  High energy (67 keV) x-ray diffuse scattering measurements were performed on
single crystals of Pb(Zn$_{1/3}$Nb$_{2/3}$)O$_3$-$x$PbTiO$_3$ (PZN-$x$PT). A
novel technique was developed to map out the diffuse scattering distribution in
all three dimensions around a large number of Bragg peaks simultaneously,
taking advantage of the almost flat Ewald sphere of the high energy x-ray beam.
For $x=0, 4.5%$, and 8%, the results are very similar, indicating same type of
correlations of polarizations in these compounds. Our results show that the
diffuse scattering intensity consists of six $<110>$ rod-type intensities
around reciprocal lattice points. These rod-type intensities are very likely
due to condensations of soft optic phonon modes, polarized in the perpendicular
$<1\bar{1}0>$ directions. A simple model is suggested where these soft phonon
modes condense into static \{110\} type planar or ``pancake'' shaped
correlations of the in-plane $<1\bar{1}0>$ polarizations.
