Prev Up Top Next Contents

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
Rock area signals have been discussed in section 4.2 .
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

We have talked about pitch undercut in section 4.1 .
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 °).


Pitch undercut


TODO: This is a list of other things that must talk about:

marco corvi - Fri May 12 21:42:40 2006
Prev Up Top Next Contents