obscured boundaries between the seen and the unseen

visual fields / fields of vision [noun] 1. all of the points of the physical environment that can be perceived by a stable eye at a given moment
2. the spaces or ranges within which objects are visible to the immobile eyes at a given time
visual percept [noun] a percept that arises from the eyes; an image in the visual system
visualization [noun] a mental image that is similar to a visual perception