Visibility function glyph not rendered in PDF

[emackey]

In section B.3.2, following #2386 and #2400, there is a glyph that renders in HTML but not in PDF.

Here's a screenshot of Specification.html:

And here's Specification.pdf:

[emackey]

@oddhack Do you happen to know any quick fix for the missing glyph here? Asciidoc source is:

glTF/specification/2.0/Specification.adoc

Line 3061 in 6014140

Introducing the visibility function latexmath:[\mathcal{V}]

[oddhack]

It is not trivial. The font used by asciidoctor-pdf when rendering math is (intentionally) incomplete - see asciidoctor/asciidoctor-pdf#1832 and related PR asciidoctor/asciidoctor-pdf#1864, wherein I got them to add the special characters needed by Vulkan to the distributed font. That took several months (some of it taken up by a long digression into licensing issues, which are resolved now), and in the meantime I was building my own fallback font with the additional characters included for use in the Vulkan build.

You could open an issue about this on their repo - it is a very small change to the build script once you know the needed Unicode value - but TBH you are probably better off just using a different character that's already in the PDF font. Maybe Greek nu (ν)? I infer the problem arose when noticing that 'V' was being used for two different things in that equation so the actual LHS is probably pretty arbitrary.

[emackey]

@oddhack Thanks as always for the insights into the documentation mechanics here, it's much appreciated!