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Optical ray tracing for luminescent materials and spectral converter photovoltaic devices

pvtrace is a statistical photon path tracer written in Python. It follows photons through a 3D scene and records their interactions with objects to build up statistical information about energy flow. This approach is particularly useful in photovoltaics and non-imaging optics where the goal is to design systems which efficiently transport light to target locations.

Interactive Jupyter notebooks examples and tutorial can be found in the docs directory.

Static versions are included in the project documentation, https://pvtrace.readthedocs.io

pvtrace was originally written to characterise the performance of Luminescent Solar Concentrators (LSC) and takes a Monte-Carlo approach to ray-tracing. Each ray is independent and can interact with objects in the scene via reflection and refraction. Objects can have different optical properties: refractive index, absorption coefficient, emission spectrum and quantum yield.

One of the key features of pvtrace is the ability to simulate re-absorption of photons in luminescent materials. This requires following thousands of rays to build intensity profiles and spectra of incoming and outgoing photons because these process cannot be approximated in a continuous way.

pvtrace may also be useful to researches or designers interested in ray-optics simulations but will be slower at running these simulations compared to other software packages because it follows each ray individually.

A minimal working example that traces a glass sphere

from pvtrace.scene.node import Node
from pvtrace.scene.scene import Scene
from pvtrace.scene.renderer import MeshcatRenderer
from pvtrace.geometry.sphere import Sphere
from pvtrace.material.dielectric import Dielectric
from pvtrace.light.light import Light
from pvtrace.algorithm import photon_tracer
import functools
import numpy as np

# Add nodes to the scene graph
world = Node(
    name="world (air)",
    geometry=Sphere(
        radius=10.0,
        material=Dielectric.air()
    )
)
sphere = Node(
    name="sphere (glass)",
    geometry=Sphere(
        radius=1.0,
        material=Dielectric.glass()
    ),
    parent=world
)
sphere.translate((0,0,2))

# Add source of photons
light = Node(
    name="Light (555nm)",
    light=Light(
        divergence_delegate=functools.partial(
            Light.cone_divergence, np.radians(20)
        )
    )
)

# Trace the scene
scene = Scene(world)
for ray in light.emit(100):
    # Do something with this optical path information
    path = photon_tracer.follow(ray, scene)

Using pip

pip install pvtrace

• python >= 3.7.2
• trimesh (for mesh shapes)
• meshcat (for visualisation)
• numpy
• anytree