<!-- Creator : groff version 1.21 -->
<!-- CreationDate: Wed Feb 9 07:50:05 2011 -->
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta name="generator" content="groff -Thtml, see www.gnu.org">
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<meta name="Content-Style" content="text/css">
<style type="text/css">
p { margin-top: 0; margin-bottom: 0; vertical-align: top }
pre { margin-top: 0; margin-bottom: 0; vertical-align: top }
table { margin-top: 0; margin-bottom: 0; vertical-align: top }
h1 { text-align: center }
</style>
<title>pic-8.html</title>
</head>
<hr>
<a href="http://validator.w3.org/check?uri=referer"><img src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01 Transitional" height="31" width="88"></a>
[ <a href="pic-7.html">prev</a> | <a href="pic-9.html">next</a> | <a href="pic.html">top</a> ]
<hr>
<h2>8. More About Direction Changes
<a name="8. More About Direction Changes"></a>
</h2>
<p style="margin-top: 1em"><font color="#000000">We’ve
already seen how to change the direction in which objects
are composed from rightwards to downwards. Here are some
more illustrative examples:</font></p>
<p align="center" style="margin-top: 1em"><font color="#000000"><img src="img/pic26.png" alt="Image img/pic26.png"></font></p>
<p align="center" style="margin-top: 1em"><font color="#000000">Figure
8-1: Effects of different motion directions (right and
left)</font></p>
<p align="center" style="margin-top: 1em"><font color="#000000"><img src="img/pic27.png" alt="Image img/pic27.png"></font></p>
<p align="center" style="margin-top: 1em"><font color="#000000">Figure
8-2: Effects of different motion directions (up and
down)</font></p>
<p style="margin-top: 1em"><font color="#000000">Something
that may appear surprising happens if you change directions
in the obvious way:</font></p>
<p align="center" style="margin-top: 1em"><font color="#000000"><img src="img/pic28.png" alt="Image img/pic28.png"></font></p>
<p align="center" style="margin-top: 1em"><font color="#000000">Figure
8-3: <b>box; arrow; circle; down; arrow;
ellipse</b></font></p>
<p style="margin-top: 1em"><font color="#000000">You might
have expected that program to yield this:</font></p>
<p align="center" style="margin-top: 1em"><font color="#000000"><img src="img/pic29.png" alt="Image img/pic29.png"></font></p>
<p align="center" style="margin-top: 1em"><font color="#000000">Figure
8-4: More intuitive?</font></p>
<p style="margin-top: 1em"><font color="#000000">But, in
fact, to get Figure 8.3 you have to do this:</font></p>
<pre style="margin-left:10%; margin-top: 1em">.PS
box;
arrow;
circle;
move to last circle .s;
down;
arrow;
ellipse
.PE</pre>
<p style="margin-top: 1em"><font color="#000000">Why is
this? Because the exit point for the current direction is
already set when you draw the object. The second arrow in
Figure 8.2 dropped downwards from the circle’s
attachment point for an object to be joined to the
right.</font></p>
<p style="margin-top: 1em"><font color="#000000">The
meaning of the command <b>move to last circle .s</b> should
be obvious. In order to see how it generalizes, we’ll
need to go into detail on two important topics; locations
and object names.</font></p>
<hr>
<a href="http://validator.w3.org/check?uri=referer"><img src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01 Transitional" height="31" width="88"></a>
[ <a href="pic-7.html">prev</a> | <a href="pic-9.html">next</a> | <a href="pic.html">top</a> ]
<hr>
