In a space where a large window/skylight is not available, the sky can be recreated, using either a camera-video projector or a camera obscura, to bring in the sky outside onto the side/ceiling of the room. Another alternative is a camera obscura room where the sky is projected on all the walls. A scale model of the camera obscura room has been constructed using a pin-hole camera to bring the sky inside the model.
With video, one has the option of projecting a previous sky on a foggy day.
The pin-hole scale model has a hole at the bottom so that one can put it over one's head to look inside, and wear it like a mask. It also functions as a portable version.
In the pin-hole scale model, the sky is in perfect focus inside. (Two pin-holes are used, a tube around one to ensure there is no overlapping.)
In the camera obscura room, the size of each hole is bigger, otherwise the image of the sky is too dim. With a bigger hole, the image of the sky is no longer in focus and a lens is needed, whose focal length is the distance between the lens and the wall. For each wall, the sky above the building is reflected by mirrors and focused onto the wall by the lens.
This camera obscura version is suitable for a location with bright light. ______________________________________________________________