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5.1 Additional topics
In this section we will talk about some topics inherent to cave map
drawing which have not been discussed so far.
5.1.1 Filled path
We did not have a chance to use a filled path.
Actually it is used just to create symbols, because it allows to fill
the area "enclosed" by the path (and the segment joining the two end-nodes
if they do not coincide) with a solid black.
As an exercise you may try to develop a symbol using the
filled path (besides the other paths).
5.1.2 Signals
Area signals can be attached to areas with connective path.
The signals are
- plan: is used for the floor of the cave
- rock: denotes a portion of rock
- hole: a hole in the passage area
- verysteep:
- dropdown:
- frame:
What do the other signals do?
According to J. Todd:
"Verysteep" does not do anythig at the moment.
Probably it will have some sort of special shading in the future.
I expect that "Dropdown" is similar.
"Frame" is about rendering other surveys into an area to make
a poster with parts of the cave visible at several scales.
Very experimental..
5.1.3 Hole area signal
"Hole" is like "rock" as far as you cannot stand there.
There is a difference however: you cannot stand on the "rock" because
there is the rock. You cannot stand in the "hole" because there is nothing.
To draw a hole in a passage that leads to a passage underneath,
draw a pit-path around the contour of the hole.
Draw an invisible line that connects the contour of the hole to the
contour of the upper passage.
Thus the area of the upper passage will not include the hole,
while the area of the lower passage will include it.
This cave map does not have any hole.
Therefore we have to practice it with a make-up hole.
The picture below shows how a hole can be drawn.
Try to draw one and see how it is rendered.
Here
is a made-up example of a south-north passage turning east, then
south, and finally to west and passing under itself
(in the east-west direction): the survex data file, "hole.svx"
is in the archive of data samples,
data.tgz
.
You can draw a hole in the upper south-north passage, connecting to the
lower east-west passage.
Open the survex file with Tunnel, set and save the XML directory, and
create a new empty sketch.
First of all you have to attach the path nodes to the centerline
(with connective paths) so that
Tunnel can know the level of the pieces of passages.
It is also important to break the passages with invisible paths
so that the portion of the upper passage with the hole is clearly
at a level above that of the lower passage.
In the picture below we have broken the wall paths inserting several nodes
and attached them
to the stations. We have also inserted a couple of invisible
lines at level -3 and -6 to make sure that the levels of the upper and
lower path are well separated.
Finally we added a connective line to the pitch area, with a "hole"
area signal. The detail render of this is shown in the second picture
below.


5.1.4 Plan area signal
What if the pit is in the lower passage?
Redraw the upper passage passing "across" the pitch.
Disconnect the pit contour from the stations in the upper passage
and connect them to the stations below. Remove the invisible
line between the pit contour and the upper wall, and insert one to
the lower wall.
If you attach a "hole" (or a "rock") area signal, the pit area will
be rendered white (the piece under the upper passage will be
slightly lighter than the rest of the lower passage), which is probably
what you do not want. So use the "plan" area signal, if you want to show
that the bottom of the pit is there.

5.1.5 Pitch undercut
The menu "Action | Pitch Undercut" creates an invisible path
that overlaps with the pit path and two zero-length lines between
the respective end-nodes. Furthemore it attaches an area signal of type
... (TODO which one?) to the zero-size area between the path.
To render the areas properly,
you must then connect the upper passage to the nodes of the pit
path, and the lower passage to the nodes of the invisible path.
When you click (Ctrl and left mouse button) on the node of a
pitch undercut you get either the node of the pit path or that
of the invisible path. If you get the wrong node, click the "delete"
button and try again. When you want to select a node at a point where
there are several nodes, every time you click Tunnel highlights
one of the nodes and a path attached to it, in round robin.
The path is useful as it helps you
to identify the node you want.
Continue to click until you get the right node.
To see which node corresponds to which path, select the path.
Tunnel highlights the pit and the invisible paths in turns.
The pit path is dashed, the invisible path is continuous.
You will see the two different nodes highlighted (pink) as squares
at different angles (0 and 45 °).

TODO: This is a list of other things that must talk about:
- area selection (Shift and right button),
what is area selection good for ?
maybe to add to subsets.
- it seems that
there is no continuation for area selection unlike for the paths.
- it is not possible to associate a symbol and a signal
to the same connective line; neither a symbol and text.
However it is possible to make
trees of connective paths and put a symbol, a signal and text at
different nodes of the tree.
FIXME: This is done !
- the types of files used by Tunnel: svx, leg, 3d (?), pos, exports,
sketch: something about this in section 2.2
- subsets: according to J. Todd, they are
labels associated to each path that can be used to change how they
are rendered, like classes and stylesheets; user interface is awful.
marco corvi - Fri May 12 21:42:40 2006
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