Extended elevation control

Assume following situation (in plan view), when there is a loop in centerline between stations 1 and 4, small chimney near station 5 and entrance to the cave is at station 6.

By default, centerline extended elevation of this situation looks this way:

This is obviously not, what we would like to have.

To control process of extended elevation, there is a special extend option in centerline command.

First of all, we would like to start our extended elevation at station 6 (where the entrance is). This can be done by specifying

extend start 6

in the centerline. Now it looks better,

but there is still problem with branch around station 5.

If we would like to start this branch from station 4, we need to forbid therion to extend station 5 from 1. This can be done by specifying

extend ignore 1 5

This means, that shot from 1 to 5 will be ignored, when extended elevation is generated.

If we would like to extend branch starting with station 5 to the left, we need to specify also

extend left 5

This will extend all stations from station 5 to the left.

As we have mentioned before, there is a small chimney above station 5. In this case, it is much more natural to draw this shot as vertical (because it is a chimney). To specify this, use

  extend vertical 5 5'

Or you can completely hide this leg from extended centerline using:

  extend hide 5 5'

Stations in extended elevation scraps

Even there is station 1 more then one time in map, therion automatically detects correct position of this station in each scrap and they are usually drawn OK.

The only think that is missing is connection line between stations 1 in these two branches. Therion does not automatically generates these lines, because their shape usually depends on the map situation.

To draw such line, all you need to do is to create a simple scrap with this line. Here is example:

scrap sc -proj extended
  point 0 0 station -name 1 -from 5 -visibility off
  point 100 0 station -name 1 -from 2 -visibility off
  line map-connection
      0   5
      0  15
    100  15
    100   5
  endline
endscrap

As you can see, even there are two stations with same name, they are distinguished by -from option, which specifies previous station in extended elevation. With this scrap, you receive final map: