Skybox images from https://learnopengl.com/img/textures/skybox.zip at
https://learnopengl.com/ (This site is a great resource not only for OpenGL,
but for 3D graphics programming in general.)


All images (and videos) are licensed under the terms of the CC BY 4.0 license
as published by Creative Commons, either version 4 of the License, or (at
your option) any later version: https://creativecommons.org/licenses/by-nc/4.0/legalcode

"When attributing any of the licensed works, please include a copyright notice
including a (hyper)link to the copyrighted work and a link to the specific
license. Please also mention my full name (Joey de Vries), this website (or a
link to the relevant article where applicable), and my personal twitter
handle: https://twitter.com/JoeyDeVriez."
