Back in the olden days, or at least before 360 photos, we simply referred to skyboxes as the way to create background imagery in computer graphics. Skyboxes depict what's far on the horizon, may contribute to the ambient lighting of the scene, be used for rendering reflections on object surfaces, and are not interactable. Unity supports skyboxes as part of the Lighting Environment for each scene. We used skyboxes already in a few of the previous chapters' projects (including Wispy Sky and Skull Platform ones).
Common sources of skyboxes are cylindrical panorama, spherical panorama (360 images), and a six-sided cube. We won't consider the cylindrical one, since it's less useful for VR.
