Monte Carlo Radiative Transfer tool
Input is the parameters file.
Example parameters.json5:
json5
{
grid: { // Output datacube settings.
boundary: { // Measurement region bounding box.
mins: [-7,-7,-7], // Domain minimum point (meters).
maxs: [ 7, 7, 7] // Domain maximum point (meters).
},
res: [101,101,101] // Grid/datacube resolution.
},
tree: { // Hit-scan performed using adaptive octave mesh.
tar_tris: 5, // Target maximum number of triangles in leaf-cells.
max_depth: 8, // Maximum splitting depth (root depth == 0).
padding: 0.01 // Multiplier to expand boxes volume when checking for contained triangles.
},
sett: { // MCRT settings.
block_size : 1000, // Number of photons to run on a thread before asking for more.
num_phot : 1e6, // Total number of photons to run.
bump_dist : 1e-6, // Distance photons are bumped past collision boundaries (meters).
loop_limit : 1e6, // Maximum number of movements a photon can make before being culled (with warning).
roulette_weight : 1e-3, // Weight at which to start playing russian-roulette.
roulette_barrels : 8, // 1.0/roulette_barrels == chance of photon surviving roulette, then weight *= roulette_barrels.
init_mat : 'air', // Initial material observed by new photons. (Detection is being stabilised).
},
surfs: { // Surfaces within the system.
plane : [['objs/plane.obj'], null], // [list of paths to base wavefront files], optional<transformation>:
cube : [['objs/cube.obj'], null], // null == no transform
cylinder : [['objs/cylinder.obj'], null], // rot: [x_axis_spin, y_axis_spin, z_axis_spin] (degrees)
square : [['objs/square.obj'], null], // scale: f64, trans: [delta_x, delta_y, delta_z] (meters)
},
attrs: { // Surface attributes.
plane : { Mirror: {} }, // Completely reflective mirror.
cube : { Refractive: { inside: 'fog', outside: 'air'} }, // Material interface (refractive), inside of mesh material, outside of mesh material.
cylinder : { Refractive: { inside: 'flesh', outside: 'fog'} },
square : { Spectrometer: {}}, // Detector surface, in this case a spectrometer. (default resolution 100, 0 - 1000nm)
},
mats: { // Material optical properties.
milk: {
Here: { // Can be written in place:
ref_index : { Constant: 1.4 }, // Refractive index.
scat_coeff : { Constant: 10.0e3 }, // Scattering coefficient (per meter).
abs_coeff : { Constant: 10.0e2 }, // Optional absorption coefficient (per meter).
// Optional shifting (Raman/fluorescence) coefficient (per meter).
asym_fact : { Constant: 0.8 } // Henyey-Greenstein asymmetry scattering factor (-1.0:1.0).
}
},
air: { There: 'mats/air.json5' }, // Or re-directed to another file.
fog: { There: 'mats/fog.json5' },
flesh: { There: 'mats/flesh.json5' }
},
light: { // Emission surface.
power : 1.0, // Source power (watts).
surf : [['objs/circle.obj'], null], // List of source surfaces.
spec : { Here: {Point: 6.3e-7}} // Emission spectrum (can be redirected to another file for complex Spectrum enumerations).
}
}
Output in the form of netcdf datacubes.
Example energy density of the above input:
