[Therion] Entering survey sketch without walls

[Bill Gee]

Thank you Bruce and Tarquin for the ideas.  I decided to make a practice 
map so I could see how all this actually works. The results are ... 
Interesting!

This zip file contains the entire project.

https://campercaver.net/MiscFiles/PracticeMine.zip

There are several versions of the map which I did as I added objects to 
it.  The last two runs are PracticeMine-4.0.pdf and PracticeMine.pdf. 
The only difference between the two is the addition of a "join" line in 
the .th file.  Wow, did that ever drive Therion crazy!

Going back to the 4.0 map - I can easily add a join between the two 
walls on the east side.  The thing I am wondering about is how the 
columns are drawn.  There is a white triangle in the middle of the map 
which show where the two scraps come together.  Two columns are split 
across the connection.  I drew them with "-outline in" on one scrap and 
did not draw them at all on the second.

If I draw only that part of the column which is in each scrap, can I 
still use "-outline in"?  Will I need to use line joins to get the two 
parts of the column to come together?  And will that result in a column 
that is entirely white on the inside?

===============
Bill Gee

On 12/3/24 13:06, Bruce Mutton wrote:
>  > using a border line instead of an invisible wall for scrap borders in 
> centre of a passage / open space
> 
> There are a number of considerations here.  This wiki post describes 
> them https://therion.speleo.sk/wiki/drawingchecklist#wall <https:// 
> therion.speleo.sk/wiki/drawingchecklist#wall>
> 
> It may be that using line wall -visibility off is a better solution than 
> either line wall -subtype invisible or line border -outline out - 
> visibility off
> 
> Tarquin’s overall approach is how I would do it.  Always end/start 
> surveys between pillars, and each open end of a scrap only joins with 
> one other scrap, to avoid the open triangle in the apparent interior of 
> the cave.  Even if you make a mistake in the field and end a survey in 
> the middle of a void far from the pillars, strategic drawing of the 
> scrap walls can mitigate the problem.  Imagine Tarquin’s sketch 
> attachment with say the left-hand survey station missing, so the station 
> joining with another survey to the left is in the centre of the void.  
> So you draw the sketch exactly as Tarquin has (with walls defining the 
> pillars at distant-left, just there is no station between them) and it 
> will work.
> 
> See also https://therion.speleo.sk/wiki/ 
> faq#how_do_i_join_three_scraps_in_a_y-shape <https://therion.speleo.sk/ 
> wiki/faq#how_do_i_join_three_scraps_in_a_y-shape>.  The XTherion 
> ‘tricky’ image demonstrates a simple case.  What is really happening is 
> that a three-scrap join is turned into a series of two-scrap joins.  
> These can then be joined semi-automatically as described in https:// 
> therion.speleo.sk/wiki/tips#joining_scraps_together <https:// 
> therion.speleo.sk/wiki/tips#joining_scraps_together>
> 
> Bruce
> 
> 
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