This simulation package interfaces NVIDIA OptiX with Geant4 to accelerate optical photon transport for physics experiments. It supports detector geometries defined in the GDML format and is based on the work by Simon Blyth, whose original Opticks framework can be found here.

Prerequisites

Before building or running this package, ensure that your system meets both the hardware and software requirements listed below.

• A CUDA-capable NVIDIA GPU

• CUDA 12+

• NVIDIA OptiX 7+

• Geant4 11+

• CMake 3.18+

• Python 3.8+

Optionally, if you plan to develop or run the simulation in a containerized environment, ensure that your system has the following tools installed:

• Docker Engine
• NVIDIA container toolkit (installation guide)

Build

git clone https://github.com/BNLNPPS/eic-opticks.git
cmake -S eic-opticks -B build
cmake --build build

Docker

Build latest eic-opticks image by hand:

docker build -t ghcr.io/bnlnpps/eic-opticks:latest https://github.com/BNLNPPS/eic-opticks.git

Build and run for development:

docker build -t ghcr.io/bnlnpps/eic-opticks:develop --target=develop .

Example commands for interactive and non-interactive tests:

docker run --rm -it -v $HOME/.Xauthority:/root/.Xauthority -e DISPLAY=$DISPLAY --net=host ghcr.io/bnlnpps/eic-opticks:develop

docker run --rm -it -v $HOME:/esi -v $HOME/eic-opticks:/src/eic-opticks -e DISPLAY=$DISPLAY -e HOME=/esi --net=host ghcr.io/bnlnpps/eic-opticks:develop

docker run ghcr.io/bnlnpps/eic-opticks bash -c 'simg4ox -g tests/geom/sphere_leak.gdml -m tests/run.mac -c sphere_leak'

Singularity

singularity run --nv -B eic-opticks-prefix/:/opt/eic-opticks -B eic-opticks:/src/eic-opticks docker://ghcr.io/bnlnpps/eic-opticks:develop

Running a test job at NERSC (Perlmutter)

To submit a test run of eic-opticks on Perlmutter, use the following example. Make sure to update any placeholder values as needed.

sbatch scripts/submit.sh

#!/bin/bash

#SBATCH -N 1                    # number of nodes
#SBATCH -C gpu                  # constraint: use GPU partition
#SBATCH -G 1                    # request 1 GPU
#SBATCH -q regular              # queue
#SBATCH -J eic-opticks          # job name
#SBATCH --mail-user=<USER_EMAIL>
#SBATCH --mail-type=ALL
#SBATCH -A m4402                # allocation account
#SBATCH -t 00:05:00             # time limit (hh:mm:ss)

# Path to your image on Perlmutter
IMAGE="docker:bnlnpps/eic-opticks:develop"
CMD='cd /src/eic-opticks && simg4ox -g $OPTICKS_HOME/tests/geom/sphere_leak.gdml -m $OPTICKS_HOME/tests/run.mac -c sphere_leak'

# Launch the container using Shifter
srun -n 1 -c 8 --cpu_bind=cores -G 1 --gpu-bind=single:1 shifter --image=$IMAGE /bin/bash -l -c "$CMD"

Optical Surface Models in Geant4

In Geant4, optical surface properties such as finish, model, and type are defined using enums in the G4OpticalSurface and G4SurfaceProperty header files:

• G4OpticalSurface.hh
• G4SurfaceProperty.hh

These enums allow users to configure how optical photons interact with surfaces, controlling behaviors like reflection, transmission, and absorption based on physical models and surface qualities. The string values corresponding to these enums (e.g. "ground", "glisur", "dielectric_dielectric") can also be used directly in GDML files when defining <opticalsurface> elements for geometry. Geant4 will parse these attributes and apply the corresponding surface behavior.

For a physics-motivated explanation of how Geant4 handles optical photon boundary interactions, refer to the Geant4 Application Developer Guide — Boundary Process.

<gdml>
  ...
  <solids>
    <opticalsurface finish="ground" model="glisur" name="medium_surface" type="dielectric_dielectric" value="1">
      <property name="EFFICIENCY" ref="EFFICIENCY_DEF"/>
      <property name="REFLECTIVITY" ref="REFLECTIVITY_DEF"/>
    </opticalsurface>
  </solids>
  ...
</gdml>