Tarquin

I think Martin is right.  And your example illustrates it well.

Your drawing shows two scraps, the red scrap should have a line at the pit of -outline out.  The green scrap should have a line at the pit of -outline out.  Outline in or outline none has no place in this example.  Whether these scrap end lines (margin between red and green) are invisible walls or pit lines is a different consideration, and could be handled a number of ways.  The line pit itself could be in either scrap (or both, but preferably not).

Maybe it is like this:

• Line orientation (yellow tick) primarily controls orientation of line ornamentation.  By convention it doubles as a way to determine the interior of an object (rock, passage) or the free-space side of the line.  Usually these two criteria correlate perfectly (think of line wall:sand or line pit), but sometimes these criteria are in conflict, and the draughtsperson needs to get creative!
• Line outline attribute is primarily for definition of the interior of a scrap.  This differs subtly from thinking of it as the interior of a passage.  Imagine a passage and oxbow.  If they are all drawn as one scrap, the interior wall must be -outline in.  If they are drawn as two or more scraps, all the walls must be -outline out.  In some cases Therion can already compensate for user error, and maybe in future it might be appropriate to automate it.
• These are two separate considerations that are (and should continue to be) handled independently (whether by the user manually or automatically by the software).

>1. Whether "-outline out" is actually the correct thing to use when the pit line points outwards rather than inwards.

As per the points above.  They are two mostly independent considerations.

>2. Why it even matters which way we draw a *wall*, if "outline out"

As you have picked, the pdf engine can solve the problem of what is the inside of a passage more often than the 3d model engines.  Perhaps in theory better coding would make the outline attribute redundant.  For now, giving users the outline attribute gives them control.

Bruce

-----Original Message-----
From: Therion <therion-bounces@speleo.sk> On Behalf Of Tarquin Wilton-Jones via Therion
Sent: Thursday, 12 December 2019 04:59
To: therion@speleo.sk
Cc: Tarquin Wilton-Jones <tarquin.wilton-jones@ntlworld.com>
Subject: Re: [Therion] Setting -outline for pit lines

> You may not specify attribute -outline in case of pit.

Why not? It is perfectly normal for a passage to end at a pit, and that pit therefore becomes a line that terminates a passage.

I have attached a hand drawn example of how this would appear normally on a plan view (at least, this is how it would normally appear on a plan survey in the UK, such as the survey of a pothole - vertical cave - like Swinsto or Simpson's).

"-outline in" does work on the pit line here for generating a PDF. But shows a warning when generating LOX.

"-outline out" also works without a warning when generating LOX or when generating PDF.

What I don't understand is

1. Whether "-outline out" is actually the correct thing to use when the pit line points outwards rather than inwards.

2. Why it even matters which way we draw a *wall*, if "outline out"

always can pick the "correct" side to fill. Surely if it can work out the "correct" side of a pit line, it can also work out the correct side of a "wall" line, and it doesn't even matter whether the yellow tick points towards "air" or "rock".

(Having to have an invisible wall on the lower scrap makes complete sense to me though, since that has to have a curved wall matching the curve of the pit line above. This is what I already use.)