[Therion] Entering survey sketch without walls

[Tarquin Wilton-Jones]

Hi Bill,

> When we start doing sketch, there will be many sections that have no 
> outside wall at all.  There will be inside wall to define the pillars. 
> Therion has a very strong dependency on walls.


If at all possible, end your surveys in passages, not at the junctions. 
Imagine a worst case scenario, where the passages (shown here in black) 
look like this, and this is the entire mine (case 1):


╋╋╋╋╋╋╋╋
╋╋╋╋╋╋╋╋
╋╋╋╋╋╋╋╋
╋╋╋╋╋╋╋╋

(Hopefully, your computer draws that as a grid of + symbols.) Always 
start and end surveys half way down a passage, so that your days' 
surveys look like this (case 2):

╋╋╋
╋╋
╋

With little stub passages coming off each junction. The worst case would 
be a very short survey that looks like this (case 3):

╋

Let's take case 3 first, which should look like a simple + symbol. That 
is a simple survey, just like any other cave. The walls just look like 
this (hopefully your computer shows a simple pair of walls with open 
ends, around the inner unshaded + symbol):

╬

That is exactly how you would normally draw a cave.

Now the problem is that Therion might see the walls being shorter than 
the open passage, so it might not know how to join the lines to fill in 
the cave properly (you will see that if you enable a background colour), 
because the walls need to be longer than the gaps at the open end of a 
passage in Therion, for it to work things out automatically. The 
solution to that is to draw an invisible wall across the open ends of 
the passages. Now that will mess up Therion's automatic scrap joins - 
which it bases on open wall ends - so I would personally use "line 
border" with "-outline out", and make it invisible. Then the wall lines 
can join another scrap's wall lines automatically. Make sense?

OK, on to case 2, assuming you draw it as a single scrap. That is the 
same basic thing, but with one inner pillar:

╬╬╬
╬╬
╬

So you just set that inner pillar's wall to "-outline in", like you 
normally would for an oxbow.

Case 1 is just case 2 with more inner walls.

Hopefully that makes sense.

The main thing for you, is to remember not to end your surveys at a 
junction, or you will hate yourself later when you get all the unpainted 
holes between your surveys (which have to be fixed with some invisible 
walls and a lot of manual line joining). End it *before* or *after* the 
junction.

Let me know if that needed clarification.

Tarquin