  Ray tracing accelerated with graphics processing units (GPUs) is an accurate
and efficient simulation technique of wireless communication channels. In this
paper, we extend a GPU-accelerated ray tracer (RT) to support the effects of
reconfigurable intelligent surfaces (RISs). To evaluate the electric field, we
derived a RIS path loss model that can be integrated into a RT and enables
further extensions for the implementation of additional features and
incorporation into complex reflective scenarios. We verify the derivation and
implementation of our model by comparison with empirical measurements in a lab
environment. We demonstrate the capabilities of our model to support
higher-order reflections from the RIS to the receiver. We find that such
components have a significant effect on the received signal strength,
concluding that the extensions of advanced functionality enabled by our model
play an important role in the accurate modeling of radio wave propagation in an
environment including RISs.
