what are the principles that govern line of sight?

[andreas]

Is there an explanation of how LOS works somewhere? I mean, of the general principles that govern whether you can see a certain square or not.

I would like, when I am in a certain situation, to be able to deduce whether or not I will be able to see another square if I am in a different spot.

(For example, it seems LOS is not preserved under rotation of the whole space, since you can see ''around corners'' if the joining hallways are vertical and horizontal, but not if they are diagonals. That's nice to know, since it allows you to killhole better; but I don't know why I should expect that to be true. Often, if the terrain is janky, I just end up relying on my (far from infallible) intuition about what we will be visible if I move in such and such a way.)

[duvessa]

(For example, it seems LOS is not preserved under rotation of the whole space, since you can see ''around corners'' if the joining hallways are vertical and horizontal, but not if they are diagonals. That's nice to know, since it allows you to killhole better; but I don't know why I should expect that to be true. Often, if the terrain is janky, I just end up relying on my (far from infallible) intuition about what we will be visible if I move in such and such a way.)

Because Crawl takes place on a grid, a diagonal hallway is not a 45-degree rotation of a horizontal one (look at the difference in wall squares required, for example).

[Rast]

[Wahaha]

Place an exclusion on a square if you want to see the los from that square.