LibreCAD Notes

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Contents:

1. LibreCAD Built-In Lettering Fonts, By Example

[NOTE TO SELF, TO DO:] The LibreCAD lettering fonts are a bit of a mess, as they're the result of a multi-decade "game of telephone" with successive translations and misinterpretations. In particular, the information supplied for the lettering alphabets derived from the Hershey Repertory is rather mangled. ("Script Complex" is a duplex face, the "scripts" is described as a Roman Simplex, the "Gothic Italian" is Hershey's Lombardic, etc.) I've got the original Hershey documentation - data and technical reports both. I need to pull them out and re-encode them, (properly documented!) from scratch in cxf and lff formats. As-is, the information in the examples below reflects that present in the LibreCAD .lff source files, and isn't quite right. (But I've got quite a lot of projects, and this one isn't at the top of the list.)

As of at least late 2014, LibreCAD supports only built-in stroke lettering. This makes perfect sense, really, as (a) it means that lettering is done simply and the letters are part of the (stroke-oriented) drawing itself rather than bitmaps or complex external vector formats, and (b) simple stroke lettering has been recommended for drafting since the early 20th century. Trying to insist on fancy type-influenced lettering is really so 19th century. :-)

The LibreCAD documentation is not, however, particularly forthcoming about what the 40 built-in stroke fonts actually are. Here they are, then, in a series of examples. I've done screengrabs here for the display, since the LibreCAD export to png, while accurate, results in minimal-width lines which do not scale well once reduced to the bitmap world.

Sheet 1: Latin alphabets in Sans Serif (i.e., traditional US Gothic), Roman, Italic, and Slanted. The notation "(H)" indicates that the lettering was derived from the Hershey repertory.

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Sheet 2: Greek and Cyrillic alphabets. The "greekc", "greekcs", "greekp" and "greeks" fonts have Greek characters in their roughly corresponding ASCII positions (not Unicode). "cyrillic_ii" has Cyrillic characters in their Unicode positions.

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"greek_ol" should be an outline font based on Kochi Gothic which has Latin characters in the regular ASCII range and Greek in the Unicode Greek range. I can't get it to work, however (although it does in QCAD Community Edition).

Note that "goth"/"gothic" in LibreCAD really means, loosely, blackletter. It is unrelated to the traditional meaning of "gothic" in American lettering and typography (where "gothic" means sans serif).

Sheet 3: Symbols. Some of these symbol sets include the Greek alphabet. In text work there is a real difference between Greek for lettering and type vs. Greek for symbols, but in the brief texts used in drafting it probably isn't important.

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"symbol_misc1" seems, on examination of the source, to include just the regular ASCII characters. The vertical alignment on "symbol_misc2" is way off.

Sheet 4: Other. The Kochi fonts have a troubled history; see the Enlish-language Wikipedia article about them.

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Here are my DXF source files for the sheets above:

The LibreCAD source files for these fonts are in the LibreCAD source/build directory: librecad/src/LibreCAD-2.0.6/unix/resources/fonts

2. ASME Y14.5M-1996 Symbols as DXF Files

Note that ASME Y14.5M-1996 has been superseded by ASME Y14.5-2009. I'm behind the times, as usual.

2.1. Lettering

The ASME Y14.5 symbols are based around the capital height of the drawing's lettering as a unit. These heights as specified in ASME Y14.2 ( Line Conventions and Lettering).

In ASME Y14.2M-1992 (which covers both inch and metric; the 'M' suffix simply indicated that it was appropriate for metric too), the heights for lettering are given as minimums, and general ("all other") lettering is the same on all sheet sizes.

The minimum size for "all other" lettering for inch drawings is: 0.12 inches.

The minimum size for "all other" lettering for inch drawings is: 3 mm.

The application of these heights to uppercase-only lettering is simple (it's the full height of the letter). Their application to lowercase lettering is more complex, but that doesn't matter here as all of the lettering to be used with Y14.5 is uppercase.

ASME Y14.2-2008 does not specify the width of the strokes in lettering. It does specify that lines should be of two widths (thin: 0.3 mm, thick 0.6 mm). In its Appendix C, which is non-normative and not part of the standard, it shows the letter stroke width and the line widths as the same.

2.2. Using these Symbols in LibreCAD

[NOT DONE]

2.3. Inch Symbols for All Sheet Sizes

[NOT DONE]

2.4. Metric Symbols for All Sheet Sizes

[NOT DONE]


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