RayTracing.jl

A high-performance Julia package for ray tracing in unstructured meshes, designed for neutron transport calculations and other particle transport simulations.

Overview

RayTracing.jl implements the Method of Characteristics (MOC) for solving the neutron transport equation. The partial integro-differential neutron transport equation can be cast as an ordinary differential equation over tracks that emulate neutron trajectories across a problem domain. This library addresses the cyclic ray tracing of those paths over any 2D rectangular mesh and computes quantities used to solve the transport equation in NeutronTransport.jl.

Key Features

• Efficient Ray Tracing: Fast generation of cyclic ray trajectories
• Unstructured Mesh Support: Works with any 2D mesh geometry
• Multiple Boundary Conditions: Vacuum, reflective, and periodic boundaries
• High-Performance Visualization: Optimized plotting recipes for large datasets
• Transport-Ready: Direct integration with neutron transport solvers

Demo

This demo showcases the ray tracing algorithm. The first animation shows ray tracing without the mesh, while the second shows ray tracing with the mesh overlay. The mesh is a simple pin-cell geometry, demonstrating how superposition of tracks over the mesh generates segments.

Installation

The package can be installed using the Julia package manager. From the Julia REPL, type ] to enter the Pkg REPL mode and run:

pkg> add RayTracing

Or, equivalently, via the Pkg API:

julia> import Pkg; Pkg.add("RayTracing")

Quick Start

using RayTracing
using GridapGmsh: GmshDiscreteModel

# Load mesh and define a model
mshfile = joinpath(@__DIR__, "demo", "pincell.msh")
model = GmshDiscreteModel(mshfile; renumber=true)

# Configure ray tracing parameters
nφ = 8   # number of azimuthal angles
δ = 2e-2 # azimuthal spacing

# Initialize track generator
tg = TrackGenerator(model, nφ, δ)

# Perform ray tracing and segmentation
trace!(tg)      # Generate tracks
segmentize!(tg) # Compute segments

Workflow

The ray tracing process consists of two main steps:

1. Track Tracing: Generate ray trajectories across the domain
2. Segmentation: Discretize tracks into segments within mesh elements

Geometry / Mesh	Tracks	Segments

Examples

Basic Usage

using RayTracing
using Gridap

# Load mesh from file
model = DiscreteModelFromFile("mesh.json")

# Configure parameters
nφ = 16  # azimuthal angles
δ = 0.08 # spacing
bcs = BoundaryConditions(top=Reflective, bottom=Reflective,
                        left=Reflective, right=Reflective)

# Create and run ray tracing
tg = TrackGenerator(model, nφ, δ, bcs=bcs)
trace!(tg)
segmentize!(tg)

# Visualize results
using Plots
plot(tg.mesh, alpha=0.3, label="Mesh")
plot!(tg, label="Tracks")

Boundary Conditions

# Reflective boundaries (rays bounce back)
bcs = BoundaryConditions(top=Reflective, bottom=Reflective,
                        left=Reflective, right=Reflective)

# Periodic boundaries (rays wrap around)
bcs = BoundaryConditions(top=Periodic, bottom=Periodic,
                        left=Periodic, right=Periodic)

# Vacuum boundaries (rays exit domain)
bcs = BoundaryConditions(top=Vacuum, bottom=Vacuum,
                        left=Vacuum, right=Vacuum)

Advanced Features

Custom Mesh Generation

Create a gmsh mesh using any available tool. Check out GridapGmsh.jl for convenience. See this example for a simple pin-cell geometry definition.

Integration with Transport Solvers

# Access segments for transport calculations
for track in tg.tracks_by_uid
    for segment in track.segments
        # Use segment.ℓ for length
        # Use segment.element for material properties
        # Use segment.p and segment.q for coordinates
    end
end

Contributing

Contributions are welcome! Please feel free to submit a Pull Request. For major changes, please open an issue first to discuss what you would like to change.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Citation

If you use RayTracing.jl in your research, please cite:

@software{raytracing_jl,
  title = {RayTracing.jl: A Julia package for ray tracing in unstructured meshes},
  author = {Vignolo, Ramiro},
  year = {2024},
  url = {https://github.com/rvignolo/RayTracing.jl}
}