UO Second Age

I am pretty sure a previous patch implemented npcs not calling guards if they had no sight of a crime being committed.

Recent los changes change this? They call guards through walls now, and you can even see their text!

It was actually the other way around. Testing on the demo, live servers, and an investigation of the scripts found that when an NPC called guards, no check was made to see if LoS was obeyed.

So why did people use bookshelves in era to block npcs from calling guards?

The only use that I have ever heard of for bookshelves was to block the ability to walk over a table wall placed in houses. At one point in time on OSI servers, certain items would raise you up their z axis when you walked on them. This allowed players to build a staircase and walk across the tops of tables which were marked as walkable surfaces on OSI servers. This was defended against by placing a row of bookshelves directly behind the tables in order to stop people from breaking into houses using this method. Beyond that, we have not seen any information that indicates any other use for bookshelves (aside from the obvious use of storage). If you can find some information that suggests that bookshelves were use for that purpose, we can put it to the test and see if and what kind of bookshelves blocked LoS.

I remember NPCs calling guards through walls, but not the ability to see their text.