2010-01-21 tikz-3dplot revisited (en)

Some time ago I wrote about a very nice 3dplot package. A few weeks later I looked into it and saw that it has one big disadvantage: the way in which you determine 3d arcs is rather useless for me, since you have to be computing a few angles manually anyway. Just a few days ago I wrote to Jeff Hein, the author of the package (which meanwhile changed its name to tikz-3dplot) and told him that I would appreciate a possibility of giving the angle as three points: the vertex and two points determining the sides of the angle. To my great surprise, within 48 hours I had an experimental—but working—version of tikz-3dplot with that very feature! I have to say that I am really, really impressed by the great work of Jeff, and tikz-3dplot will be an indispensable tool for me. It is a really great joy to see software development like this!

CategoryBlog, CategoryEnglish, CategoryTeX, CategoryLaTeX, KategoriaLaTeX

Komentarze na tej stronie

2010-01-15 Customizing end-of-proof marks (en)

I was recently asked by a friend to help him with customizing end-of-proof marks. Say that we are writing a textbook with theorems with proofs and example problems with solutions and that we want a usual after a proof, but, for example, a after a solution to a problem.

Probably the best way to accomplish this is by using the powerful ntheorem package by Wolfgang May and Andreas Schedler (see its home page). But alas, I don’t usually use it (since I am used to amsthm), which is a shame on me: ntheorem seems to do all the work of amsthm and much more. The only problem is that you have at least to skim through the documentation (which is well written and not too long) – I am quite busy now, but hopefully I will be able to read it in a few weeks’ time and write something about it here.

If you are an amsthm-addict for some reason, there is also hope for you: just use the following quick-and-dirty solution (to be pasted in the preamble):

\newenvironment{solution}{%
  \proof[Solution]\def\qedsymbol{$\diamond$}%
}{%
  \endproof
}

What it does is:

1. The newly-defined environment solution will launch the proof environment whenever \begin{solution} is put into the document. Roughly speaking, \proof is (almost) the same as \begin{proof}.
2. The \qedsymbol will be redefined into whatever we want (here, the ). Since we don’t use LaTeX’s \newcommand, but plain TeX’s \def, this redefinition is local, i.e., valid only within the proof environment.
3. The \end{solution} is defined to be essentially the same as \end{proof} ; note that \endproof is a “low-level version” (again, roughly speaking!) of \end{proof}.

Summing up: the main purpose of this construct is to teach people something (hopefully) interesting about how TeX and LaTeX works; for production purposes, ntheorem is better.

CategoryBlog, CategoryEnglish, CategoryTeX, CategoryLaTeX, KategoriaLaTeX

Komentarze na tej stronie

2009-11-19 The 3dplot package (en)

It’s been quite a lot of time since I’ve written anything here; I hope that I will be able to put things more often at this blog. But ad rem.

Today I looked at http://www.texample.net/tikz/, which is a very good place to look at for all fans of tikz (like me), and found something really, really great: an example of a very new 3dplot package (links to the package and docs are under that link). There were two features I miss from tikz: easy Bézier curves like in Metapost (i.e., without having to state the control points explicitly) and three-dimiensional arcs. Well, there is only one left (the former one).

What’s the point? Especially when you typeset educational materials (and I do it from time to time), you may want to draw a picture of some geometrical solid. The tikz package lets you draw points in 3d space in an isometric view very easily, so it’s not a problem—at least, until you want to have an angle, usually denoted by an arc, in your picture. Obviously, under an affine transformation, an arc of the circle becomes some arc of some ellipse, and calculating which one is rather tedious. The 3dplot package does it for you! (I haven’t tried it yet, but I will do it for sure when I need such a feature, which probably means next few weeks.)

Many, many kudos to Jeff Hein for this one!

CategoryBlog, CategoryEnglish, CategoryTeX, CategoryLaTeX, KategoriaLaTeX

Komentarze na tej stronie