[Therion] Setting -outline for pit lines

[Tarquin Wilton-Jones]

>     By convention it doubles as a way to determine
>     the interior of an object (rock, passage) or the free-space side of
>     the line.

Thank you!

This seems to have sealed the idea in my head. It's a convention because
it matters with some ornamentations. And it almost always makes sense
because the tick points towards "air". Except when it's a boulder. ;)

> As you have picked, the pdf engine can solve the problem of what is the
> inside of a passage

Since the line's orientation has little/no effect on where the engine
chooses to decide is the "inside" of a structure, this makes me wonder ...

Maybe there is a possibility that I can construct a cave where the
proximity of openings/entrances and passage curves will cause it to
construct the passage on the wrong side of a line. And in such a case,
the solution would be to make invisible walls. Interesting. I will
probably randomly bump into that, one day.

Anyway, thanks for explaining it to me.