[Therion] New symbols

[Bruce Mutton]

As far as I can see, it's all related to the order you choose to apply the transformations. I used the align before the rotate. If you move the align to be done after the rotate the behaviour changes. Maybe you could test a little bit and propose a better order for the transformations after testing several use cases.

Yes, if you swap align and rotate, all becomes well.  I did quite a lot of testing.  Read all of this wiki section Symbol Sizing and Positioning <https://therion.speleo.sk/wiki/metapost#symbol_sizing_and_positioning> 

 

> 5.  Points that can be aligned , have their (non-zero) rotation corrupted when they are both rotated and aligned.  You can see in the example that the speleothem points have been aligned bottom-right, when the th2 file says they should be aligned right).  This problem exists with all (almost) existing Therion points.  I have identified the cause and proposed a solution here https://therion.speleo.sk/wiki/metapost#symbol_sizing_and_positioning but my metapost skills are very basic, so no doubt it could be improved upon.

 

I'm not sure I fully understand your issue. The result for rotated and right aligned symbols seemed more intuitive to me when I inverted the align and the rotate transformations in symbols. I bet that would be a nice change but I wonder if you are talking about something more subtle that I have not fully understood yet.

I think you have understood what I am referring to.  The situation where this is most apparent and vexing in a real cave drawing is when using a point water-flow, or point air-draught entering or leaving a passage (perpendicular to a wall).  You want to align the symbol so that it plots correctly at a variety of scales, but invoking the alignment makes it displace in entirely the wrong direction.  It at first appears to be random, because it depends entirely on the value of the rotation option.  But this is a live problem (bug) for almost every point symbol currently in Therion.

 

Oops, I have messed up.  I did not test the information in the wiki post sufficiently, six months ago when I wrote it, and just made the assumption that I had fixed a Therion symbol alignment problem that I had noticed.  In fact, I just changed the problem.  So my coloured words in the boxed text above are wrong, and the wiki post is only partly correct.

 



So if you are looking at the lower diagram in the wiki post and trying to make sense of it, don’t worry, it is wrong and the pictures show that it is wrong!

There are SOME Therion point symbols that do not align correctly, but it is not a general problem (of course, someone would have noticed it before now).  My proposed solution in the wiki post is therefore not right, and actually makes the problem worse.

I think I know what to do now, but won’t have time for a while.

 

Symbols that align the wrong way include water-flow and air-draught.  There is also something amiss with the alignment of speleothem symbols, but it is not of the same nature.  Eventually I will have a go at fixing it, but not for some time. Maybe I will put together an example file to demonstrate the issue first, so that I can be sure second time around that it is solved.

 

Sorry about any confusion caused.

Bruce

 

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