  We discuss an implementation of our 3D radiative transfer (3DRT) framework
with the OpenCL paradigm for general GPU computing. We implement the kernel for
solving the 3DRT problem in Cartesian coordinates with periodic boundary
conditions in the horizontal $(x,y)$ plane, including the construction of the
nearest neighbor $\Lstar$ and the operator splitting step. We present the
results of a small and a large test case and compare the timing of the 3DRT
calculations for serial CPUs and various GPUs. The latest available GPUs can
lead to significant speedups for both small and large grids compared to serial
(single core) computations.
