[Therion] Custom map connections

[Bruce Mutton]

Tarquin

I don't have a solution to your particular question, but for what it is
worth here is my map-connection journey so far.

 



The default point map-connection lines are all but invisible in large maps,
and there is no orientation that shows clearly what is the offset and what
is the main map.



So I modified the l-arrow and l-map-connection metapost.  These are clearly
visible and have a clear orientation - dot in the main map and arrowhead at
the offset position.



My convention is to place a map-connection point at every location where a
caver could travel from the main map to the offset map. This makes an
easy-to-follow map where there are just a few, but not so much when there
are many.



Then I discovered the ICCaving Migovec project that uses a user-defined
point u:connection.  These are just coloured dots that must be manually
placed in each offset map.  There are no lines joining the dots.  This
approach avoids the noise associated with lots of connecting lines and has
the advantages of working across various projections and being able to
adjust the colour and size on a point-by-point basis.  It is not so obvious
which is the primary map and which is offset though.  My work-in-progress
example does not show it at its best.

 

I haven't settled on a favourite approach yet, it probably depends on the
particular cave.  Both approaches need further development.

I like your suggestion that Therion be able to pass an object id and user
defined attribute as it will add to the options available.

 

Bruce

 

-----Original Message-----
From: Therion <therion-bounces at speleo.sk> On Behalf Of Tarquin Wilton-Jones
via Therion
Sent: Friday, 8 July 2022 05:04
To: Therion <therion at speleo.sk>
Cc: Tarquin Wilton-Jones <tarquin.wilton-jones at ntlworld.com>
Subject: [Therion] Custom map connections

 

Hi folks,

 

I have a challenge, presented to me by some users of one of our surveys.

 

We have a cave with layers horribly stacked above each other (10 passages
all crossing the same point!). Simple solution; use map offsets to put them
all side by side. Use map connection arrows to show what connects to what.

 

That's all good, but they find the default connection arrow hard to see.

I can redefine l_mapconnection to create my own arrows. Great!

 

But here's the challenge; they want us to show the difference between an
unimportant connection, and a major "follow this route" connection. Eg.

minor ones in grey, major route in red.

 

I have tried everything I can think of with the mapconnection point: id,
scale, rotation, -attr etc., but Therion is not creating a p_mapconnection.
it creates a l_mapconnection, and passes it a path to create the line. The
attributes are all completely ignored.

 

Normally, I would use "-attr type major", but that cannot work here, because
Therion just ignores it. In my opinion, this is a limitation that should be
fixed.

 

The only solution I can think of, is to put *two* mapconnection points.

The l_mapconnection code can then see if the current path matches the
previous path, and if so, draw it in red. But this is such a horrible hack,
and prone to failure in future if someone does not realise why there are two
points, and why they have to follow on from each other.

 

Can anyone think of a better workaround?

 

Cheers,

 

Tarquin

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