[Therion] Surface or Canyon walls

[Duncan Collis]

On 15/02/2017, Martin Sluka via Therion <therion at speleo.sk> wrote:
>
>> 14. 2. 2017 v 19:30, Bruce Mutton via Therion <therion at speleo.sk
>> <mailto:therion at speleo.sk>>:
>> are used by the scrap join algorithm to decide which line ends to join
>> (for visible wall lines only),
>
> For automatic scrap join algorithm. But you may join any kind of lines at
> any line points - typically wall to corner of block

It's worth noting that there are two different ways of making a wall
line invisible in Therion, which are treated differently by the
automatic scrap join algorithm:

line wall -subtype invisible
   The wall line is not displayed, and will be ignored by the scrap
join algorithm.

lne wall -visibility off
   The wall line is not displayed, but can be used by the scrap join
algorithm when it chooses which points to join.

This caused me a fair amount of confusion until I figured it out!

Duncan.