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May 8 – 12, 2023
Norfolk Waterside Marriott
US/Eastern timezone

Opticks : GPU Optical Photon Simulation using NVIDIA OptiX 7 and NVIDIA CUDA

May 8, 2023, 12:15 PM
Marriott Ballroom VII (Norfolk Waterside Marriott)

Marriott Ballroom VII

Norfolk Waterside Marriott

235 East Main Street Norfolk, VA 23510


Dr Lin, Tao (IHEP)


Opticks is an open source project that accelerates optical photon simulation by
integrating NVIDIA GPU ray tracing, accessed via the NVIDIA OptiX 7 API, with
Geant4 toolkit based simulations. A single NVIDIA Turing architecture GPU has
been measured to provide optical photon simulation speedup factors exceeding
1500 times single threaded Geant4 with a full JUNO analytic GPU geometry
automatically translated from the Geant4 geometry. Optical physics processes of
scattering, absorption, scintillator reemission and boundary processes are
implemented in CUDA based on Geant4. 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.

In this work we describe the near complete re-implementation of geometry and
optical simulation required to adopt the entirely new NVIDIA OptiX 7 API, with
the implementation now directly CUDA based with OptiX usage restricted to
providing intersects. The new Opticks features a modular many small header
design that provides fine grained testing both on GPU and CPU as well as
substantial code reductions from CPU/GPU sharing. Enhanced modularity has
enabled CSG tree generalization to support "list-nodes", similar to
G4MultiUnion, that improve performance for complex CSG solids. Recent addition
of support for interference effects in boundaries with multiple thin layers,
such as anti-reflection coatings and photocathodes, using CUDA compatible
transfer matrix method (TMM) calculations of reflectance, transmittance and
absorptance is also reported.

Consider for long presentation Yes

Primary authors

Presentation materials

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