  Optical photon propagation is an embarrassingly parallel operation, well
suited to acceleration on GPU devices. Rendering of images employs similar
techniques -- for this reason, a pipeline to offload optical photon propagation
from Geant4 to the industry-standard open-source renderer Mitsuba3 has been
devised. With the creation of a dedicated plugin for single point multi-source
emission, we find a photon propagation rate of $2\times10^{5}$ photons per
second per CPU thread using LLVM and $1.2\times10^{6}$ photons per second per
GPU using CUDA. This represents a speed-up of 70 on CPU and 400 on GPU over
Geant4 and is competitive with other similar applications. The potential for
further applications is discussed.
