I want to check if a certain point or box in space (3D) is completely surrounded by faces (e.g. rectangles), so that this point or box is not visible from any location with a certain minimum distance.
Do you know of such an algorithm?
To make it clearer:
Imagine a minecraft style game. There may be caves in the underground, but when you're outside the cave, and the cave does not have any entrance, anything in the cave cannot be seen, from no direction. I want to detect if something is inside such a "cave", so it doesn't need to be rendered (unless you drill a hole and enter the cave).