Therion and DistoX Training Course Guide - 6) Adding additional scraps

Adding additional scraps

Our cave has a passage coming from under part of the chamber and up into the chamber through a hole in the floor. We cannot include both this passage and the chamber in one scrap because a single scrap is not allowed to include overlapping passages. So in this lesson we will learn how to add additional scraps into our drawing. Once you can do this you will be able to draw up surveys for even the largest cave systems.

There is no reason not to draw multiple scraps in the same drawing file, unless it is becoming difficult to see what is happening in the editor. Therion will render the final survey the same whether the scraps are in one or several .th2 files. For our cave we will draw the new scrap in the file we are already using for the chamber. Start by inserting a new scrap by clicking the toolbar button (or press Ctrl+r). Name the scrap ‘bpwSP2’ and set the projection to ‘plan’ following the same steps as we covered in lesson 3.

If you look at the ‘Objects’ information panel at the top of the right hand pane, you should see there are now two scraps defined. Each starts with a line ‘scrap - <name>’ where <name> is the name of the scrap, and ends with the line ‘end scrap’. All the objects in each scrap appear between these lines. So our new scrap contains nothing at the moment. If you select one of the start lines for a scrap then everything in that scrap is coloured blue in the map editor. Select the ‘scrap - bpwSP2’ line and everything should turn yellow in the drawing because nothing is in this scrap yet. Now the new scrap is selected in the objects window, any new lines or points we draw will be put into the new scrap. Start by adding a couple of survey station points so that Therion will know where to place the scrap on the survey. The procedure is exactly the same as we covered in lesson 3. Next draw the wall lines and the floor step. Remember to check that the ticks on the wall lines point into the passage, and that the tick on the floor step points down the drop. This should be enough for now to add the new scrap into the survey. Here is how our scrap looks in the map editor.

Switch to the text editor and add the new scrap into the map:

  map bpwMP
bpwSP1
bpwSP2
endmap

Now compile the project again to see how it looks. You should see that the floor step line has been clipped because it curves outside the area bounded by the two wall lines. To fix this step the option ‘-clip off’ for the floor step line. The plan survey drawing should look better now, but the passage passing underneath the floor of the chamber is not shown underneath. We need to break the map into two parts so that Therion renders one scrap over the top of the other. This is done by adding the word ‘break’ in between the two scraps in the map.

  map bpwMP
bpwSP1
break
bpwSP2
endmap

Here is now this should have rendered.

Now the floor step appears greyed out when the pit where the passage goes off is actually in the chamber floor. So we will move the floor step line into the chamber scrap. Select the floor step line and then look at the ‘Objects’ information panel. We want to move it from the position in the second scrap to inside the first scrap. Find the line number of the ‘end scrap’ line for the first scrap, enter that number into the box next to the ‘Move to’ button and click the button. The line should have been moved up to above the ‘end scrap’ line for the first scrap. You can select the scraps in turn by clicking on the ‘Select next scrap’ button in the toolbar above. Now the floor step line should be rendering in the finished drawing as solid black. Ideally we should also draw the opposite side of the pit to clearly indicate that this side passage enters up from a hole in the floor.

Finally in this lesson a quick note on pillars or loops in passages. We will extend the passage in our new scrap to include a loop to illustrate this. Here is what we will draw.

Note the rock pillar, or loop in the cave passage highlighted in red. When we compile this we do not get a green OK bar on the compiler page. Instead the bar stays Orange and displays ‘Warning’. This is telling us that Therion issued a warning. We can find it in the log file produced with the other output files. The file is called ‘therion.log’. Open this file in a text editor and search for the word ‘warning’. You should find the following:

  “warning -- bpwSP2@bpw -- multiple scrap outer outlines not supported yet”

The warning tells us which object caused the warning. This is where our naming convention for objects really helps us, because we can tell it is in a plan scrap (SP) in the part of the cave named bpw. For really big caves with many scraps this will help identify where the problem is. In this case it is our new scrap, and the warning is because our scrap has two outlines. One is the rock outside the passage, and the other is the pillar of rock inside the loop in the passage. If we look at the 3D model (.lox file) we see that this part of the model does not look right. The walls in this scrap are not showing up in the model as expected. The way to fix this is to indicate that the lines making up the inside of the loop are surrounding a section of rock inside the outer boundary of the cave walls in this scrap. We do this by adding the text ‘-outline in’ to the options field for the wall line inside the loop. Compile the project again and this time the warning is not generated and the 3D model shows the walls correctly.