mainpix.html

有限元学习研究用源代码(老外的),供科研人员参考

<title>IBG: Using a Pixmap as Geometry Description</title>

<H1>Using a Pixmap as Geometry Description</H1>

 <P>To use graphical input for the description of complex 2D
geometries is an interesting possibility of <A HREF="ibg.html">IBG</A>.

 <P>The <A HREF="examples.html">example</A> file <A
HREF="../examples/mainpix.c">mainpix.c</A> creates a 2D grid using the
pixmap <A HREF="../test/test.ppm">test.ppm</A>. To create this
program, simply

<PRE>
make pix
</PRE>

 <P>The picture is assumed to describe the geometry by using a single
color for each region.

 <P>Example: R黦en Island (Germany):
 <br> <IMG ALT="R&uuml;gen" SRC="ruegen_grid.gif"> <br>


 <P>This test picture I have created in the following way:

 <UL>

 <LI> A <A HREF="ruegen.gif">picture</A> of the region around
R&uuml;gen was obtained with the <A
HREF="http://pubweb.parc.xerox.com/map">Xerox PARC Map Viewer</A> and
the xv grab function.

 <LI> xpaint was used to manipulate this picture:

 <UL>
 <LI> At first, a <A HREF="ruegen2col.gif">picture</A> which contains
only two colors was created.

 <LI> The two segments have been subdivided into six more convex
subsegments with slightly different colors. This technique allows to
avoid topological errors for very small islands.

 </UL>

 <LI> The resulting <A HREF="../test/test.ppm">picture</A> has been
saved in the PPM format.

 </UL>