Box shaped artificial skies are constructed in shape of prism, which represents endless outdoor space due to multiple reflections on mirror walls. Small box shaped models are usually used to measure side-lighted  models , while the window opening has to be situated only within one external wall. The model is connected with the box shaped artificial sky by the wall with window.

▼ Croghan, D. Daylighting by design. Version 1.3., Cambridge, July 2015.
(Croghan D, ‘Daylighting Buildings’ (technical papers 1964-1970).pdf)

▼Hopkinson, R.G., Petherbrige,P. Longnore, J. Daylighting. London: Heinemann, 1966.