November 2019 - Therion

Metapost for a line ending in an ellipse
by Tarquin Wilton-Jones 24 Nov '19

24 Nov '19

Hi all, One of the common symbols used in rigging topos is a deviation. It looks like a solid line, ending with a horizontal ellipse. (The rope would then pass through the centre of the ellipse, which is why it helps to have a line point within the centre of the ellipse, to make it easy to line them up with each other.) __ ----(__) In Therion's Metapost, the line is easy; pickup PenC; thdraw P; Drawing a horizontal ellipse at the coordinates of the last point in the line is easy: p:=fullcircle xscaled (.5u) yscaled (.25u); draw p shifted (point (length P) of P); But making the last "leg" of the line stop at the point where it intersects the ellipse ... I am baffled. One method would be; work out the angle of the last part of the line, work out the radius of the ellipse on that angle. Draw the line from the previous point to the length minus the last "radius" length. That's all fair and good, but when the line is curving, the radius of the ellipse at the final direction where the line ends, and the radius where the line enters the ellipse is different, and therefore the length of the undrawn part of the line is wrong. See the attached picture; the one with the straight line is right, the one with the curved line is wrong - the blue line should not be drawn inside the ellipse. Blue = what I am drawing. Yellow = line points. Green = parts that would be not drawn using the method described above. I am guessing the maths required to calculate the final length of the line is horrendously complicated (but please tell me if I am wrong). Is there maybe another way? Can I say "draw the line, erase the line within the area of this elliptical 'circle', draw this elliptical 'circle'", in that sequence? Thanks for any assistance you can provide. Tarquin

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scaling a line thickness in Metapost
by Tarquin Wilton-Jones 24 Nov '19

24 Nov '19

I want to be able to select a different thickness of line for different "scale" values that can be selected in the .th2 file. Lines can have a scale like this, which seems perfect for what I need: -scale xs * Is there a way to access this value from within a custom line definition like this? def l_u_foo (expr P)= if ATTR_scale ... * Assuming it can be seen from some ATTR value, internal variabe or function parameter, what values will it see for the various -scale options (xs, s, m, l, xl) - if it is a number, what are the numeric values for the various scales, or if it is a string, does it just see the literal values "xs", "s" etc.? Cheers! Tarquin

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Export Multiple Caves to Single KML Model
by Bruce Mutton 22 Nov '19

22 Nov '19

> There is one feature I have found that does not work. . One of my four maps has a section where two passages run pretty much the same way, one directly above the other. In the single-cave map I handled this by setting the upper passage off to the side. That does not come through to the group map. The two passages are drawn on top of each other. Bill I presume you are now referring to exported map pdf outputs? I was looking for something that fitted that description in an old copy of your Big Cavern Ranch project that I got from one of your posts last year, but didn't find anything. In general, if you select and export a map that has offsets defined, they will be honoured. I you do not specifically select a map with the offsets defined, then the scraps will be plotted in their true position - no offset. I do this intentionally for overview maps of multiple caves, as offsets at small scales (1:2,000, 1:10,000) provide a misleading impression of the cave. It seems like you have done this as well, perhaps unwittingly. Your source BigCavernRanch.th contains a survey named 'all' but there is no corresponding map defined as far as I can see. Therefore despite each of those caves referenced having maps defined, they are not used - every scrap defined is used instead. So no offsets. >From the Therion Book. 'select' Description: selects objects (surveys and maps) for export. By default, all survey objects are selected. If there is no map selected, all scraps belonging to selected surveys are selected by default for map export. You can easily control what is plotted by defining a 'map all' in your BigCavernRanch.th file (or elsewhere) and then selecting it in your 'all' thconfig. Bruce

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metapost input file
by Andrew Atkinson 13 Nov '19

13 Nov '19

My layouts for my areas has become difficult to manage, especially all the metapost. input file works in metapost, but requires the full path, is there a way to find the path of the file that you are in and us that as a base. We use version control so different machines have different file paths, so really want to avoid this. At the moment I have make a different file for my symbols and in each file have to have a layout/endlayout and code metapost/endcode, then in the master file I have to input outside the layout and then copy the layout for each file, which works but it would be so much nicer to just have input symbol.mp inside the one code metapost/ endcode thanks Andrew

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***UNCHECKED*** Scrap with no stations give unhelpful error message
by Bruce Mutton 04 Nov '19

04 Nov '19

If a map export to pdf is attempted at too large a scale, we get the error; Therion\therion.exe: error -- scrap scrap609@ defined at 1-BigEntrance.th2 [4135] is too large to process in metapost in this scale -- maximal scale for this scrap is 1 : 336 This I am familiar with, and know how to deal with. It is because the maximum 'size' of a pdf output can be 5m x 5m or thereabouts. If we try too small a scale, we get a similarly helpful error message. Therion\therion.exe: error -- thconfig.thc [20] -- thconfig.thc [20] -- scale out of range -- 1 5000000000 Again, the error message is explicit and helpful. If there is a scrap with no stations, then the error message is; Therion\therion.exe: error -- Map is too large for PDF format. Try smaller scale! To save the user searching for a scale that works it would be helpful to change this error message to "scrap has no point stations defined - cannot be scaled". Bruce

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Horrific Warping between maps where I want my lines to join
by alastair gott 03 Nov '19

03 Nov '19

Hi Therion Mailing List, My maps are just not joining where I want them to, the walls are repellant to each other! All I want to do is join the black line where i'm putting the red line, but the yellow warping lines are thrusting it away again. If anyone has any thoughts it would be great to know them because there's something fundamentally wrong with what I'm doing! [cid:206d78da-11f6-41f7-b5bf-6b26829ce45f] Regards, Alastair Gott. AlastairGott(a)hotmail.com, M: 07931779380.

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