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nLab > Latest Changes: New SVGs for knot pages

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    • CommentRowNumber1.
    • CommentAuthorAndrew Stacey
    • CommentTimeOct 14th 2010

    Using the LaTeX macro package TikZ, I’ve redrawn most of the SVGs on the knots and links pages. I hope that I haven’t trodden on any toes in so doing! I may have missed a few diagrams as well.

    I’ve shifted the actual SVGs to pages of their own. This makes it easier to edit the pages with them on - TikZ’s SVG export isn’t as compact as the inbuilt SVG editor - and easier to include on other pages. For example, I can imagine that the trefoil knot is going to appear again and again!

    (Incidentally, are the two trefoils distinct? If so, which have I drawn at trefoil knot - SVG).

    I’ve named the pages with - SVG in their name, though for the moment I’ve also put in redirects to the name without the SVG. When actually including the diagram, one should always use the canonical name (ie with the - SVG) since it may be that we actually write a page about the trefoil knot one day. But I thought that for the moment, a nice aspect of hyperlinks is that if we mention the trefoil knot in a page then we can put in a link to an actual picture.

    Diagrams done so far:

    Pages with includes include: link, Reidemeister move, colorability, bridge number.

    What would be fantastic here is if the “source” link took one to the actual LaTeX/TikZ source! I do intend to put that up on the nLab, but I need to clean it up a little as it depends on some customised style files that have a lot of crud in them.

    • CommentRowNumber2.
    • CommentAuthorEric
    • CommentTimeOct 14th 2010

    Cool. I was thinking about adding “category: svg” to these pages, but then would it should up on each page it was included? Would that be a bad thing?

    • CommentRowNumber3.
    • CommentAuthorTim_Porter
    • CommentTimeOct 14th 2010

    Thanks, Andrew.

    Don’t worry about toes!

    There are two types of ambient isotopy one is general the other is orientation preserving (so includes mirror images). The two trefoils are mirros of each other and are not oriented isotopic. Strangely enough the figure 8 is isotopic to its mirror.

    I agree about the spelling of Reidemeister!

    • CommentRowNumber4.
    • CommentAuthorMike Shulman
    • CommentTimeOct 14th 2010

    How does one export to SVG from TikZ? I remember trying to figure this out a while ago and not being very successful.

    • CommentRowNumber5.
    • CommentAuthorAndrew Stacey
    • CommentTimeOct 14th 2010
    • (edited Oct 14th 2010)

    For these pictures, I just added the line:

     \def\pgfsysdriver{pgfsys-tex4ht.def}

    before the \usepackage{tikz} line then ran htlatex on the document. That spat out the pictures as SVGs. I’m using the latest TikZ/PGF which I downloaded from http://www.texample.net. From reading the manual, it seems that the exporter works best for pictures without complicated text - like knot diagrams!

    • CommentRowNumber6.
    • CommentAuthorTobyBartels
    • CommentTimeOct 15th 2010
    • (edited Oct 15th 2010)

    Andrew wrote:

    I’ve also put in redirects to the name without the SVG

    Redirects in included pages act pretty weird. Check out trefoil knot, for example. Rather than redirecting to trefoil knot - SVG, it redirects (for now) to bridge number. That should be because bridge number was the last page to be edited that included trefoil knot - SVG.

    Since you can’t use such redirects for inclusion either, all in all I consider them useless. So in light of the above, I think that they should be deprecated.

    Eric wrote:

    I was thinking about adding “category: svg” to these pages, but then would it should up on each page it was included?

    Yes, it would! It’s the same basic idea as with the redirects.

    • CommentRowNumber7.
    • CommentAuthorAndrew Stacey
    • CommentTimeOct 15th 2010

    I didn’t know that. That’s very useful to know!

    But keeping the same functionality isn’t actually all that hard. We make a page “trefoil knot” with the contents:

    [[!include trefoil knot - SVG]]

[[!redirects Trefoil Knot]]
...

    We could also do the category: svg manually. The point of doing it manually (apart from not messing up included pages) would be that we can then list both the SVG and its source (and maybe PDF and PNG versions) altogether.

    • CommentRowNumber8.
    • CommentAuthorTobyBartels
    • CommentTimeOct 17th 2010

    We make a page “trefoil knot” with the contents:

    [[!include trefoil knot - SVG]]

[[!redirects Trefoil Knot]]
...

    Certainly, once we make trefoil knot. But Trefoil Knot shouldn’t redirect anywhere until then. (Well, for now they both redirect to knot, which I guess is OK.)

    We could also do the category: svg manually.

    I don’t understand that.

    • CommentRowNumber9.
    • CommentAuthorAndrew Stacey
    • CommentTimeOct 18th 2010

    Right, I’ve fixed the knots and their SVGs, so that we now have trefoil knot, Hopf link, Borromean link, Whitehead link, and figure eight knot.

    The best way to explain what I meant about doing “category: svg” manually is probably to show you, so here it is at SVG images.

    • CommentRowNumber10.
    • CommentAuthorTobyBartels
    • CommentTimeOct 21st 2010

    Ah, make a list manually! Yes, certainly that is good to do.

    And I will put that list in category: meta. (^_^)

    • CommentRowNumber11.
    • CommentAuthorTobyBartels
    • CommentTimeOct 21st 2010

    You still have a redirect from Borromean rings - SVG to Borromean link - SVG. This does not work; click on the link here to see. Because your intended target is included in Borromean link and that was edited more recently, that is where the redirect goes.

    • CommentRowNumber12.
    • CommentAuthorAndrew Stacey
    • CommentTimeOct 21st 2010

    Oh …. bother. Fixed it.

    So the rule is that included pages should have no redirects or category information therein since they get applied to any including pages as well. In case of categories, that’s just annoying, in case of redirects, it can break the intention.

    Hmm, I’m going to file this as a feature request. If I write a page and put it in a category and add some redirects, then you decide that you want that as a subsection of a bigger page, then all my redirects now break. That seems unfortunate behaviour.

    • CommentRowNumber13.
    • CommentAuthorTobyBartels
    • CommentTimeOct 21st 2010
    • (edited Oct 21st 2010)

    I broke it again so that Jacques can see it. (I also made a trivial edit to Borromean link to break it thoroughly.)

    Edit: H’m, that didn’t actually break it properly. The rule for which page becomes the redirect target must be something other than which page was last edited.

    • CommentRowNumber14.
    • CommentAuthorTobyBartels
    • CommentTimeOct 28th 2010

    As Jacques has implemented our feature request, I have restored category: svg.

    • CommentRowNumber15.
    • CommentAuthorTim_Porter
    • CommentTimeOct 29th 2010

    I have done a diagram at knot group. I used Inkscape, but cannot get the arrowheads to appear (the intention is an arrow on the underpass going up) and I cannot get the labels x ix_i to work. (I am used to xfig where you can edit the code to produce latex labels. Is that possible within SVG?)

    • CommentRowNumber16.
    • CommentAuthorAndrew Stacey
    • CommentTimeNov 11th 2010

    For some reason, the arrowheads are getting removed by the XHTML sanitiser on Instiki. I don’t know why the bit of syntax that puts them on is not allowed, but it seems to be with how Inkscape specifies its arrowheads. I’ll investigate further.

    • CommentRowNumber17.
    • CommentAuthorTim_Porter
    • CommentTimeSep 10th 2012

    At colorable knot, I am having a formatting problem. The SVG of the figure 8 knot is within an examples environment and the system throws the heading of the example after the picture. Can someone explain what I am doing wrong? :-(

    • CommentRowNumber18.
    • CommentAuthorTim_Porter
    • CommentTimeSep 10th 2012
    • (edited Sep 10th 2012)

    Ah that’s better. How did you do that? but at the moment it is still not 100% right. :-)

    (Edit: slightly later. TA! Diolch)

    • CommentRowNumber19.
    • CommentAuthorAndrew Stacey
    • CommentTimeSep 10th 2012

    The problem was on the SVG page. Included pages get included as they are, which means that they don’t necessarily inherit the indentation of where they are being included. Blank lines, in particular, can cause problems. So I changed the SVG so that it was all on one line. Makes it hard to read, but then who is really going to read an SVG?

    The bizarre behaviour is because the heading is actually inserted after the page loads by a bit of javascript which looks for a suitable place to insert it. Clearly in this case it was finding the wrong place - I’ll investigate why and let Jacques know.

    What’s still not right about it?

    • CommentRowNumber20.
    • CommentAuthorTim_Porter
    • CommentTimeSep 10th 2012

    There was an interim situation that came up when I reloaded, in which the part below the diagram was in a blue shaded box. That has gone and it looks great now.

    • CommentRowNumber21.
    • CommentAuthorAndrew Stacey
    • CommentTimeSep 10th 2012

    Ah, right. Yes, that was me messing about in boats. Or code.

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