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--- tips [2019/12/10 11:17] – [Joining scraps together] warning when use join command sluka
+++ tips [2020/01/13 16:32] – clip also affects layering tarquinwj
@@ Line 131: / Line 131: @@
 As described in the Therion Book, __How the map is put together__, the layers are 'default-bottom', 'default' and 'default-top'.  'Default', as you might guess is in the middle. Areas go to the bottom, ceiling-step and chimney go to the top, everything else is somewhere in the middle.
-Now if you find that you have not drawn an entity in exactly the right order to get that special effect you were after, there is an over-ride.  There are two more 'layers', 'top', and 'bottom' and these are placed by Therion above 'default-top' and below 'default-bottom' respectively.  To put an entity in either of these layers, add the option -place top or -place bottom.  If using -place for an area it is probably a good idea to use -place for its defining border as well.
+Now if you find that you have not drawn an entity in exactly the right order to get that special effect you were after, there is an over-ride.  There are two more 'layers', 'top', and 'bottom' and these are placed by Therion above 'default-top' and below 'default-bottom' respectively.  To put an entity in either of these layers, add the option -place top or -place bottom.  If using -place for an area it is probably a good idea to use -place for its defining border as well. There is then an upper layer on top of 'top', which is the layer containing any items that have '-clip off', since these are rendered after all items that take part in normal clipping. If you have an entity without '-clip off' that needs to be rendered on top of an entity that has '-clip off' (eg. a ceiling step that must appear on top of a boulder when the boulder-edge has '-clip off'), then you will need to give the first entity (the ceiling step in the example) '-clip off' as well. These non-clipped entities are then layered with respect to each other respecting the usual -place and stacking orders.
 Fifthly, transparency and opacity settings come into it, as well as the particular viewer or printer driver you are using, as indicated in the first paragraph above.
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 ====Joining scraps together====
-**Warning:** Use command **join** ONLY in case it is necessary - when two scraps both have open ends which is needed to connect/join. Don't use command **join** when there are not open ends (line **wall**, etc.) in those scraps. For example when there are two underlying scraps connected with pit. Note: Theoretically it is not correct from point of view of drawing maps, but it is very often case in cave maps. You may use more complicated command **join** to connect end of line from one scrap to point or point of line from second scrap.\\
+One of Therion's key features is that drawings are created in small pieces - scraps. A scrap is the smallest indivisible part of the drawing that can exported to create an output.\\
+Most maps contain many scraps, and if they don't happen to appear perfectly joined by coincidence, then you should "join" these individual scraps to get Therion to morph them together. \\
+''**Important:** Only use the **join** command if it is necessary to do so. ie when there are open passage ends or drawing lines that should be joined in the final output, but are not. \\
-One of Therion's key features is that drawings are created in small pieces - scraps. A scrap is the smallest indivisible part of the drawing that can exported to create an output.\\
+**Do not use** the **join** command if your adjacent scraps do not have any lines that need to be joined.  An example of this would be a higher passage approaching the top of a pitch, and a lower passage that continues from the bottom of the pitch.  Both the upper scrap and the lower scrap might be drawn with closed ends around the top and bottom of the shaft respectively.  These overlapping scraps would not normally need to be joined, and using the semi-automatic approach described below will guarantee extreme distortion!''\\
-Most maps contain many scraps, and if they don't happen to appear perfectly joined by coincidence, then you should "join" these individual scraps to get Therion to morph them together. There are three ways to do it; fully automatically in *.th2 file, semi-automatically scrap by scrap, and manually line by line (if you must specify exactly which lines and points join). The last two are described in Thbook;
+**How to join scraps**
+There are three ways to join scraps, or components of scraps;
+  * fully automatically in *.th2 file,
+  * semi-automatically scrap by scrap, and
+  * manually line or point by point (if you must specify exactly which lines and points join).
+For any particular pair of lines or points to be joined, you should only use one of these methods.  Multiple joins of the same set of objects is likely to give unpredictable results! The last two methods are described in Thbook and all three are described below.\\
-Join commands are put directly into the survey section, not inside any scrap or map definitions - lines are joined independently, ignoring whatever scraps and maps they are defined or included in.
+Join commands can be put directly into a survey definition, but not usually inside scrap or map definitions.
 **Fully automatic in *.th2 file**
-If you draw two or more scraps adjacent to each other in your drawing *.th2 file, and make sure the adjacent line wall ends snap to each other, then Therion will automatically morph them, if necessary, to create a perfect join.  A morph might be necessary, if for example survey closure or other drawing distortions might tend to separate the scraps you have drawn as touching.
+If you draw two or more scraps adjacent to each other in your drawing *.th2 file, and make sure the adjacent line wall ends snap to each other, then Therion will automatically morph them, if necessary, to create a perfect join.  A morph might be necessary, if for example survey closure or other drawing distortions might tend to separate the scraps you have drawn as touching.\\
+This is really just an automatic implementation of the 'Manual line or point by point' method described below.
 **Semi-automatic scrap by scrap**
@@ Line 199: / Line 210: @@
     join scrap1 scrap2 [-count <number of passage (not line) joins for Therion to look for>]
-The method can only join two scraps at a time.  Note that it only works using passages defined by lines of "wall" type (even if their "-outline" is set to "none"). It does not join other types of line. It normally expects to find pairs of lines, one on each side of the passage opening. If there are multiple places where the two scraps join, you can normally use the "-count" option to say how many possible passage joins Therion should search for in the two scraps.
+The method can only join two scraps at a time.  Note that it only works using passages defined by lines of "wall" type (even if their "-outline" is set to "none"). It does not join other types of line. It normally expects to find pairs of lines, one on each side of the passage opening. If there are multiple places where the two scraps join, you can normally use the "-count" option to say how many possible passage joins Therion should search for and join in the two scraps.
-**Manual line by line**
+**Manual line or point by point**
-From time to time the semi-automatic way does not work, or you want more refined control.  Then you should join each line to the other line (usually, but not only walls) or to a point. If you have several objects to join at one point, then unlike the scrap by scrap join above, you should use one join statement to join them all (see bottom of this topic).  Every point on a line has a mark according its sequence from beginning of line (yellow tick). The first one has mark 0, next one 1, etc., last one is mark "end". So the join command will be:\\
+From time to time the semi-automatic way does not work, or you want more refined control.  Then you should join each line or point to the other line or point (usually, but not only walls). If you have several objects to join at one point, then unlike the scrap by scrap join above, you should use one join statement to join them all in one go (see bottom of this topic).  Every point on a line has a mark according its sequence from beginning of line (yellow tick). The first one has mark 0, next one 1, etc., last one is mark "end". So the join command will be:\\