maincharfunctest.html

Delaunay三角形的网格剖分程序

<TITLE>COG 2.1: Charfunction for regions</TITLE>
<PRE>
#include "<A HREF="coglib.hxx">cog/coglib.hxx</A>"
</PRE>

<H1>Defining Regions by Characteristic Function</H1>

 <P>A region may be defined by their <B>characteristic function</B>
which is &gt; 0 in the region and &le; 0 outside.  For example, to
define the region in this picture:
 <P><IMG SRC="charfunctest.gif">
 <P>we can use the following simple function:

<PRE>
wzFloat hyperbel(const wzPoint&amp; p)
{
  return (p[0]+0.05)*(p[0]+0.05) - 4*(p[1]-0.5)*(p[1]-0.5);
}
</PRE>

 <P>There are also a lot of <A HREF="mainfunctiontest.html">other
possibilities to define functions</A>, especially functions defined on
grids.  Now we define a simple octree grid generator and define this
function <I>hyperbel</I> on it's geometry
 <A HREF="mainfunctiontest.html">as usual</A>:

<PRE>
int main()
{
  cogenOctree base = new CogenOctree();
  base-&gt;setBorder(0.0,1.0, 0.0,1.0);
  wzRegion inner_box = wzRegion(2);
  base-&gt;addBox(inner_box, 0.1,0.9, 0.1,0.9);
  cogeometry geom0 = base-&gt;geometry();
  wzIndex    place = 0;
  cogeometry geomf = new CogeometryFunctionOnRegions(geom0,hyperbel,place);
</PRE>

 <P>Now we have to create the geometry defined by this characteristic function:

<PRE>
  wzFloat level = 0.03;
  CogeometryCharFunction* geom = new CogeometryCharFunction
	(geomf,wzRegion(3),place,level);
</PRE>

 <P>We want to use the characteristic function only inside the <I>inner_box</I>:

<PRE>
  geom-&gt;inRegion(inner_box);
</PRE>

 <P>What remains is standard:

<PRE>
  base-&gt;refinementGlobal(0.1,0.05);
  wzgrid grid = (*base)(geom);
  grid-&gt;write("test.sg");
}
</PRE>