mainuniontest.html

Delaunay三角形的网格剖分程序

<TITLE>COG 2.1: Unions</TITLE>

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<H1>Unions</H1>

 <P>Now, let's consider how to define unions of the simple geometries
we are already able to define: combine geometries defined in different
coordinates:

 <P><IMG SRC="uniontest.gif">
 <IMG SRC="union1test.gif">
 <IMG SRC="union2test.gif">

 <P>Now, a key concept of COG becomes important: the independence
between geometry description and grid generation.  Until now, there
was a very close connection between the geometry and the resulting
grid.  

 <P>Now it becomes important to understand that the connection is not
as strong as it seems to be.  The geometry is always global.  The grid
may be defined only on a part of the global geometry.

 <P>First, let's create two test generators - one with curved
geometry, another with rectangular geometry:

<PRE>
#include "<A HREF="coglib.hxx">cog/coglib.hxx</A>"
int main()
{
  cogenOctree base = new CogenOctree();
  base-&gt;addBox(wzRegion(1), 0.15,0.4,-1.5,1.5);
  base-&gt;addBox(wzRegion(2), 0.2,0.3);
</PRE>

 <P>Note the "global" character of region 4: we have not given
y-values, thus, the geometry definition is unbounded, defines the
whole ring. This defines the circle on the right half.

 <P>But the box for the grid generation (implicitly defined by the
first call as [0.15,0.4]x[-1.5,1.5]) is not modified.  Thus, only in
the left half polar coordinates will be choosen.

<PRE>
  base-&gt;faceRefinementGlobal(0.02,0.5);
  base-&gt;refinementGlobal(0.05,0.15);
  cogenRefine base_ref = new CogenRefine(base-&gt;generator());
  base_ref-&gt;refinementInRegion(0.02,0.3,1.0,wzRegion(2));
  base_ref-&gt;refinementNearFace(0.002,0.3,0, wzFace(1));

  wz2dmap cpolar = new wz2Dpolar;
  cogenChart polar = new CogenChart(base_ref-&gt;generator(),cpolar);

  cogenOctree ortho = new CogenOctree;
  wzIndex i1 = ortho-&gt;addBox(wzRegion(1),-0.4,0.4,-0.5,0.5);
  wzIndex i2 = ortho-&gt;addBox(wzRegion(3),-0.05,0.05);
  ortho-&gt;setFaceOfBox(wzFace(1),i1);
  ortho-&gt;setFaceOfBox(wzFace(3),i2);

//  cogenRefine ortho_ref = new CogenRefine(ortho-&gt;generator());
  ortho-&gt;refinementGlobal(0.05,0.05);
  ortho-&gt;faceRefinementGlobal(0.005,1.0);
</PRE>

 <P>Now, we define a union and add these two generators:

<PRE>
  cogenComposite gen = new CogenUnion;
  gen-&gt;add(polar-&gt;generator());
//  gen-&gt;add(ortho_ref-&gt;generator());
  gen-&gt;add(ortho-&gt;generator());
</PRE>

 <P>That's all.

 <P>Note that the first set of coordinates will be preferred in its
own box. (Try out how changing the order modifies the grid!)

 <P>Instead, in the geometry the region with higher region number is
preferred. That's why the ring (region 4) is hidden behind the bar
(region 6).

<PRE>
  wzgrid grid = (*gen)();
  grid->write("test.sg");
}
</PRE>