sightline

noun

1. A line between an observer or a piece of optical equipment and an object of interest; line of sight.

   “This area, referred to as the fly loft, should typically be two and a half times taller than the proscenium opening in order to fly the scenery above the vertical sightlines of the first row of the audience.”

   “They drove on, every rise in the road lifting their sightline clear of the drystone dykes along the roadside, gifting glimpses of the firth and the islands, the blue peaks of Arran.”

   “It became a popular garden plant in the 20th century, when a Chinese variant (Buddleia Davidii ^([sic])) was introduced. That's when the trouble started. The plant has spread like wildfire since. Its fast-growing invasive nature and survivability is a huge problem for the railways, as (left alone) it can cause serious, expensive damage to structures, block drivers sightlines, or pose a risk to lineside workers.”