little_helpers/tikz/sketch-0.2.161/Doc/sketch/Hello-world.html

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  13 Copyright (C) 2005, 2006, 2007, 2008 Eugene K. Ressler.
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  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
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  56 <h3 class="section">2.1 Hello world</h3>
  57
  58 <p>The <code>sketch</code> program above is nearly the simplest one possible,
  59 the equivalent of a &ldquo;hello world&rdquo;
  60 <a name="index-hello-world-5"></a><a name="index-program_002c-hello-world-6"></a>program you might find at the start of a programming language text.
  61 If it is saved in the file <span class="file">simple.sk</span>, then the command
  62 <a name="index-command-line_002c-_0040code_007bsketch_007d-7"></a><a name="index-running-_0040code_007bsketch_007d-8"></a>
  63 <pre class="verbatim">
  64   sketch simple.sk -o simple.tex
  65 </pre>
  66 creates a file <span class="file">simple.tex</span> containing <code>PSTricks</code> commands to
  67 draw these objects on paper.  The contents of <span class="file">simple.tex</span>
  68 look like this.
  69 <pre class="verbatim">
  70   \begin{pspicture}(-1,-1)(2,2)
  71   \pstVerb{1 setlinejoin}
  72   \psline(-1,-1)(.333,.333)
  73   \pspolygon[fillstyle=solid,fillcolor=white](0,0)(1,0)(0,1)
  74   \psline(.333,.333)(2,2)
  75   \end{pspicture}
  76 </pre>
  77 The hidden surface algorithm
  78 <a name="index-hidden-surface-algorithm-9"></a>of <code>sketch</code> has split
  79 <a name="index-splitting_002c-line-and-surface-10"></a>the line into
  80 two pieces and ordered the three resulting objects so that the correct
  81 portion of the line is hidden.
  82
  83    <p>If you've noticed that the projection we are using seems equivalent to
  84 erasing the z-coordinate of the three-dimensional input points,
  85 pat yourself on the back.  You are correct.  This is called a
  86 <dfn>parallel projection</dfn>.
  87 <a name="index-parallel-projection-11"></a><a name="index-projection_002c-parallel-12"></a>The z-coordinate axis is pointing straight out of the paper at
  88 us, while the x- and y-axes point to the right and up as
  89 usual.
  90
  91    <p>The resulting picture file can be included in a LaTeX document with
  92 <tt>\input{simple}</tt>.  Alternately, adding the command line option
  93 <span class="option">-T</span><a rel="footnote" href="#fn-1" name="fnd-1"><sup>1</sup></a>
  94 <a name="index-command-line-option-13"></a><a name="index-option_002c-command-line-14"></a>causes the <code>pspicture</code> to be wrapped in a short
  95 but complete document, ready to run though LaTeX.
  96 <a name="index-document-template-15"></a><a name="index-template_002c-document-16"></a>In a finished, typeset document, the picture looks like this.  (The
  97 axes have been added in light gray.)
  98
  99 <div align="center"><img src="ex020.png" alt="ex020.png"></div>
 100
 101 <p class="noindent">It is important to know that only the &ldquo;outside&rdquo;
 102 <a name="index-outside-of-a-polygon-17"></a><a name="index-polygon_002c-outside-of-18"></a>of a polygon is
 103 normally drawn.  The <dfn>outside</dfn> is where the vertices given in the
 104 <code>polygon</code>
 105 <a name="index-polygon-19"></a>command appear in <em>counter-clockwise</em>
 106 <a name="index-counter_002dclockwise-polygon-vertex-order-20"></a><a name="index-polygon-vertex-order-21"></a><a name="index-order_002c-polygon-vertex-22"></a>order.  Thus, if the command above had been
 107 <pre class="verbatim">
 108   polygon(0,1,0)(1,0,0)(0,0,1)
 109 </pre>
 110 the polygon would not appear in the picture at all.  It would have
 111 been <dfn>culled</dfn>
 112 <a name="index-culling-23"></a>from the scene.  This culling behavior may seem
 113 strange, but stay tuned.
 114
 115    <div class="footnote">
 116 <hr>
 117 <h4>Footnotes</h4><p class="footnote"><small>[<a name="fn-1" href="#fnd-1">1</a>]</small> Or for European users of A4 size paper,
 118 <span class="option">-Te</span>.</p>
 119
 120    <p><hr></div>
 121
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 123