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A package providing radiance, polarisation, and transmittance information from the daylight.

Project description

The skylight project GitHub top language GitHub license GitHub last-commit Build Status


This Python package implements three models that provide skylight information.

1. The Prague sky model

This model (proposed by Vévoda P. et al., 2022; original C++ code here) interpolates the skylight properties by using stored data for a range of parameters, and it does not include data for the angle of polarisation (this is calculated by using the analytical solution).


There are three available datasets that work with the Prague Sky Model, which can be downloaded form here:

2. Analytic sky model

This model (proposed by Wilkie A. et al., 2004; and Preetham A. J. et al., 1999) includes radiance and polarisation information.


3. Uniform model

This model provides the same information for any sky conditions and viewing directions, and it could be used as a baseline model.



You can easily install the package by using pip as:

pip install git+

Alternatively you need to clone the GitHub repository, navigate to the main directory of the project, install the dependencies and finally the package itself. Here is an example code that installs the package:

  1. Clone this repo.
mkdir ~/src
cd ~/src
git clone
cd sky
  1. Install the required libraries.
    1. using pip :

      pip install -r requirements.txt
    2. using conda :

      conda env create -f environment.yml
      conda activate sky-env
  2. Install the package.
    1. using pip :
      pip install .
    2. using conda :
      conda install .

Note that the pip project might be needed for the above installation.

Graphical User Interface (GUI)

If you prefer to use a graphical user interface for this package, there is a separate package that you can install and use. This is named the sky-gui and it allows for interactive exploration of the skylight properties for the different models. However, in this version, only the Prague Sky Model is supported.


Report an issue

If you have any issues installing or using the package, you can report it here.


The code is written by Evripidis Gkanias.


The original (C++) code for this model was written by Petr Vévoda et al. from Alexander Wilkie's group in Charles University, which was part of their wide spectral range sky radiance model.


Copyright © 2022, Evripidis Gkanias; Institute of Perception, Action and Behaviour; School of Informatics; the University of Edinburgh.

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