Opticks is an open source project that integrates the NVIDIA OptiX
GPU ray tracing engine with Geant4 toolkit based simulations.
Massive parallelism brings drastic performance improvements with optical photon simulation speedup expected to exceed 1000 times Geant4 with workstation GPUs.
Optical physics processes of scattering, absorption, reemission and
boundary processes are implemented as CUDA OptiX programs based on the Geant4
implementations. Wavelength dependent material and surface properties as well as inverse cumulative distribution functions for reemission are interleaved into
GPU textures providing fast interpolated property lookup or wavelength generation.
OptiX handles the creation and application of a choice of acceleration structures
such as boundary volume hierarchies and the transparent use of multiple GPUs.
A major recent advance is the implementation of GPU ray tracing of complex constructive solid geometry shapes, enabling automated translation of Geant4 geometries to the GPU without approximation. Using common initial photons and random number sequences allows the Opticks and Geant4 simulations to be run point-by-point aligned. Aligned running has reached near perfect equivalence with test geometries.