[Therion] FW: How to draw flooded passages

Bruce bruce at tomo.co.nz
Tue Nov 1 07:11:47 CET 2011


I got a little bit interested in your inquiry as shown in the attached
therion dataset.  The pdf files show the results of changing various
parameters.  This is a bit rambling and perhaps lacks direction, but maybe
it is of use to someone.

The transparency or otherwise of particular entities depends on;

-mainly the symbol definition (does it have an opaque background written
into the definition?),

-then the transparency and opacity settings used in the layout,

-placement (top, bottom) and order in which it is drawn in the individual

-and probably some other things I haven't thought of.

The first symbols drawn tend to be placed at the bottom.  As you draw each
symbol tends to overlie the ones previously drawn.  If you look at the th2
file with a text editor you will see that as you draw, each item is entered
before the previous item; so as with map definitions, the first entities in
the file are on top of the ones further down.

If you check in the therion book "How the map is put together" you will see
that it is really more complicated than this and that therion anticipates
that some types of entities are usually above other types regardless of
their placement in the file.

You can modify this a little by using -place top or -place bottom on a case
by case basis.  In practice I find that if you are fussy, fine adjustment
takes a lot of experimentation.  Still, in general I think it is a good idea
to draw things at the bottom first (the sump area fill) and things near the
top last (the water fill - which is how an airbell will look).

I have experimented with two ways of drawing area water over area sump (near
stations B6 & B7).  The area associated with border id l26-543-625 made me
think that enabling line border to have -outline [out in none] (similar to
walls) would make definitions of areas (associated those borders) with holes
in them easier to draw.  Low priority as there is a workable but slightly
more complicated alternative for the draughtsperson as in the attached.

I always use purpose drawn line border as a boundary for fills, as this
minimises problems with areas becoming disassociated from there borders if
lines are split in two during subsequent edits.

border             # I tend to use this to define area water
border:invisible   # I tend to use this to define area sump

Which brings me to a question. 
Why are some borders to water areas in my example thick & some thin?
The borders near B5, B6, B7 & B8 should all be the same, but B6 is thinner?
This sort of thing in the past has been due to bugs in the symbol
definitions in metapost.  Only thing is that it is happening with both the
default symbols and with my custom symbols, so to me that points to a
problem with my drawing of the scraps - cannot find it though!


>I'm trying to draw cave passage which are mainly
>flooded but have a few places where you can surface due to air filed domes.
>See http://static.23.nu/md/Pictures/ZZ6E08C628.png - the orange parts are
>the ones where we can breathe air.

>How do I draw something like this? Two layers, or an area where we can
>surface? If so which kind of area is preferred?

>Maximillian Dornseif

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