little_helpers/tikz/sketch-0.2.161/Doc/sketch/Special-objects.html

   1 <html lang="en">
   2 <head>
   3 <title>Special objects - Sketch</title>
   4 <meta http-equiv="Content-Type" content="text/html">
   5 <meta name="description" content="Sketch">
   6 <meta name="generator" content="makeinfo 4.7">
   7 <link title="Top" rel="start" href="index.html#Top">
   8 <link rel="up" href="Introduction-by-example.html#Introduction-by-example" title="Introduction by example">
   9 <link rel="prev" href="Drawing-a-solid.html#Drawing-a-solid" title="Drawing a solid">
  10 <link rel="next" href="Object-transforms.html#Object-transforms" title="Object transforms">
  11 <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
  12 <!--
  13 Copyright (C) 2005, 2006, 2007, 2008 Eugene K. Ressler.
  14
  15 This manual is for `sketch', version 0.2 (build 161),
  16 Tuesday, September 08, 2009, a program that converts descriptions of simple
  17 three-dimensional scenes into static drawings. This version generates
  18 `PSTricks' or `PGF/TikZ' code suitable for use with the
  19 TeX document processing system.
  20
  21 `Sketch' is free software; you can redistribute it and/or modify
  22 it under the terms of the GNU General Public License as published by
  23 the Free Software Foundation; either version 3, or (at your option)
  24 any later version.
  25
  26 Sketch is distributed in the hope that it will be useful,
  27 but WITHOUT ANY WARRANTY; without even the implied warranty of
  28 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  29 GNU General Public License for more details.
  30
  31 You should have received a copy of the GNU General Public License
  32 along with `sketch'; see the file COPYING.txt.  If not, see
  33 http://www.gnu.org/copyleft.-->
  34 <meta http-equiv="Content-Style-Type" content="text/css">
  35 <style type="text/css"><!--
  36   pre.display { font-family:inherit }
  37   pre.format  { font-family:inherit }
  38   pre.smalldisplay { font-family:inherit; font-size:smaller }
  39   pre.smallformat  { font-family:inherit; font-size:smaller }
  40   pre.smallexample { font-size:smaller }
  41   pre.smalllisp    { font-size:smaller }
  42   span.sc { font-variant:small-caps }
  43   span.roman { font-family: serif; font-weight: normal; }
  44 --></style>
  45 </head>
  46 <body>
  47 <div class="node">
  48 <p>
  49 <a name="Special-objects"></a>Next:&nbsp;<a rel="next" accesskey="n" href="Object-transforms.html#Object-transforms">Object transforms</a>,
  50 Previous:&nbsp;<a rel="previous" accesskey="p" href="Drawing-a-solid.html#Drawing-a-solid">Drawing a solid</a>,
  51 Up:&nbsp;<a rel="up" accesskey="u" href="Introduction-by-example.html#Introduction-by-example">Introduction by example</a>
  52 <hr><br>
  53 </div>
  54
  55 <!-- node-name,  next,  previous,  up -->
  56 <h3 class="section">2.4 Special objects</h3>
  57
  58 <p>We can add labels
  59 <a name="index-labels-47"></a>to a drawing by using <tt>special</tt>
  60 <a name="index-special-48"></a><a name="index-special-object-49"></a>objects, which provide a way to embed raw LaTeX and <code>PSTricks</code>
  61 code.  Adding this to the tetrahedron does the trick.
  62 <pre class="verbatim">
  63   special |\footnotesize
  64            \uput{2pt}[ur]#1{$P1$}
  65            \uput[r]#2{$P2$}
  66            \uput[u]#3{$P3$}
  67            \uput[d]#4{$P4$}|
  68     (p1)(p2)(p3)(p4)
  69 </pre>
  70 Here is the result.
  71
  72 <div align="center"><img src="ex042.png" alt="ex042.png"></div>
  73
  74    <p>There are several details to note here.  First, the quoting convention
  75 <a name="index-quoting_002c-special-50"></a>for the raw code is similar to the LaTeX <tt>\verb</tt> command.  The
  76 first non-white space character following <tt>special</tt> is
  77 understood to be the quote character,
  78 in this case <span class="samp">|</span>.  The raw
  79 text continues until this character recurs.
  80
  81    <p>Second, the argument references
  82 <a name="index-argument_002c-special-51"></a><tt>#1</tt>, <tt>#2</tt>, <tt>#3</tt>,
  83 and <tt>#4</tt> refer to points in the list that follow.  This is
  84 similar to TeX macro syntax.  The transformed and two-dimensional
  85 projections of these three-dimensional points are substituted
  86 <a name="index-substitution_002c-special-52"></a><a name="index-special-argument-substitution-53"></a>in the final output.  An argument reference of the form <tt>#1-2</tt>
  87 is replaced with the angle in degrees of the two-dimensional vector
  88 that connects the projections of the two respective argument points,
  89 here <tt>#1</tt> and <tt>#2</tt>.  The substituted angle is enclosed
  90 in curly braces <code>{ }</code>
  91
  92    <p>By default, <code>special</code> objects are printed last, overlaying all
  93 other objects in the scene.  If you specify the internal option
  94 <a name="index-internal-option-54"></a><a name="index-option_002c-internal-55"></a><code>lay=in</code>, the hidden surface algorithm
  95 <a name="index-lay-56"></a><a name="index-hidden-surface-algorithm-57"></a>considers the entire special object to be the first point
  96 (<tt>#1</tt>) in the argument list.  If that point is behind (of
  97 smaller z-component than) any drawable, then the entire special
  98 object is drawn before that drawable, so the drawable obscures parts of
  99 the special object that overlaps it.  In our example, <tt>p1</tt> is
 100 the front-most point in the scene (has the largest
 101 z-component), so adding <code>lay=in</code> has no effect.
 102
 103    <p>With option <code>lay=under</code>, a special is drawn <em>before</em>, hence
 104 appears <em>under</em> any of the objects handled by the hidden surface
 105 algorithm.  This is how the light gray axes were added to the &ldquo;hello
 106 world&rdquo; example <a href="Hello-world.html#Hello-world">Hello world</a>.
 107
 108    <p><tt>Special</tt> objects are powerful, with many possible uses.
 109
 110    </body></html>
 111