PyViewFactor

pyViewFactor is a lightweight open-source Python library for exact view-factor computations on polygonal meshes. It provides robust tools for:

• geometric visibility analysis,
• obstruction detection,
• accurate view factor computation.

Full documentation available at arep-dev.gitlab.io/pyViewFactor.

Features

• This library enables the computation of radiation view factors between planar polygons using an accurate double‐contour integration method described in (Mazumder and Ravishankar 2012) with insights from (Schmid 2016).
• It uses the handy Pyvista package to deal with geometry imports (*.stl, *.vtk, *.obj, ...), geometry creations, and some other mesh functionalities under the hood.
• It enables:
  • 🔺 View factor computation between planar polygons via the SA-30 semi-analytic kernel — handles touching and coplanar faces analytically, no epsilon shift
  • 👁️ Visibility checks based on face orientation
  • 🚧 Obstruction detection using Möller–Trumbore ray-triangle intersection, BVH-accelerated (O(log N) per ray)
  • ⚙️ Strict / non-strict modes for robustness control
  • ⚡ Full N×N view-factor matrix with Numba prange parallelism (~33× faster than v1.0)
  • 📦 Built on numpy, scipy, pyvista, numba

Installation

pyViewFactor can be installed from PyPi using pip on Python >= 3.10:

pip install pyviewfactor

You can also visit PyPi or Gitlab to download the sources.

Requirements:

numpy==1.26.4
pyvista==0.45
scipy==1.11.4
numba==0.61.2
tqdm==4.65.0

The code will probably work with lower versions of the required packages, however this has not been tested.

[!NOTE] numba is optional but strongly recommended. Without it, all kernels fall back to sequential pure-Python with identical results — no need to pin an older version.

Quick Start

Suppose we want to compute the radiation view factor between a triangle and a rectangle facing each other:

You are few lines of code away from your first view factor computation:

import pyvista as pv
import pyviewfactor as pvf

# Create a rectangle and a triangle facing each other
pointa1 = [0.0, 0.0, 0.0]
pointb1 = [1.0, 0.0, 0.0]
pointc1 = [0.0, 1.0, 0.0]
rectangle = pv.Rectangle([pointa1, pointb1, pointc1])

pointa2 = [0.0, 0.0, 1.0]
pointb2 = [0.0, 1.0, 1.0]
pointc2 = [1.0, 1.0, 1.0]
triangle = pv.Triangle([pointa2, pointb2, pointc2])

if pvf.get_visibility(rectangle, triangle)[0]:
    F = pvf.compute_viewfactor(triangle, rectangle)
    print("VF from rectangle to triangle :", F)
else:
    print("Not facing each other")

pl = pv.Plotter()
pl.add_mesh(rectangle, color="lightblue", opacity=0.7)
pl.add_mesh(triangle, color="salmon", opacity=0.7)

# compute and glyph normals for mesh1
n1 = rectangle.compute_normals(cell_normals=True, point_normals=False)
arrows1 = n1.glyph(orient="Normals", factor=0.1)
pl.add_mesh(arrows1, color="blue")
# similarly for mesh2
n2 = triangle.compute_normals(cell_normals=True, point_normals=False)
arrows2 = n2.glyph(orient="Normals", factor=0.1)
pl.add_mesh(arrows2, color="darkred")

pl.show()

You want to import your own geometry from a different format? (*.dat, *.idf, *.stl, ...)

Check pyvista's documentation on how to generate a PolyData facet from points.

Documentation

For detailed explanations and advanced usage, see:

https://arep-dev.gitlab.io/pyViewFactor/

The documentation includes:

• Theory: view factor integral, SA-30 semi-analytic kernel, BVH obstruction engine,
• Implementation: architecture, visibility & obstruction semantics, performance guide,
• Extended examples with analytical validations.

Citation & Acknowledgments

• Main contributors:
  • Mateusz BOGDAN,
  • Edouard WALTHER.
• Acknowledgment: The authors would like to acknowledge M. Alecian for his initial work on the quadrature code and M. Chapon for her contribution to the code validation.

There is even a conference paper, showing analytical validations.

So if you use pyViewFactor in your work, please cite:

[!IMPORTANT] Citation: Mateusz BOGDAN, Edouard WALTHER, Marc ALECIAN and Mina CHAPON. Calcul des facteurs de forme entre polygones - Application à la thermique urbaine et aux études de confort. IBPSA France 2022, Châlons-en-Champagne.

Bibtex entry:

@inproceedings{pyViewFactor22bogdan,
  author       = "Mateusz BOGDAN and Edouard WALTHER and Marc ALECIAN and Mina CHAPON",
  title        = "Calcul des facteurs de forme entre polygones - Application à la thermique urbaine et aux études de confort",
  year         = "2022",
  organization = "IBPSA France",
  venue        = "Châlons-en-Champagne, France"
  note         = "IBPSA France 2022",
}

License

MIT License - Copyright (c) AREP 2025