mainoctreereftest.html

Delaunay三角形的网格剖分程序

<TITLE>COG 2.1: Refinement in a box</TITLE>

<H1>Refinement in a Box</H1>

 <P><IMG SRC="octreereftest.gif">

 <P>Some possibilities for refinement are already defined for the
class <B>CogenOctree</B> - it is homogeneous refinement and refinement
inside a box.  Let's start with the simple octree example used in the
 <A HREF="mainreftest.html">general local refinement example</A>:

<PRE>
#include "<A HREF="coglib.hxx">cog/coglib.hxx</A>"
int main()
{
  cogenOctree gen = new CogenOctree();
  wzIndex i1 = gen-&gt;addBox(wzRegion(2), 0.0,1.0,0.0,1.0);
  wzIndex i2 = gen-&gt;addBox(wzRegion(3), 0.1,0.2, 0.7,0.9);
  wzIndex i3 = gen-&gt;addBox(wzRegion(3), 0.3,0.4, 0.6,0.8);
  wzIndex i4 = gen-&gt;addBox(wzRegion(4), 0.7,0.9, 0.1,0.5);
</PRE>

 <P>The only difference as far is that we get identifiers for the
boxes <i>i1, i2, i3, i4</i>.  These identifiers may be used to define
isotropical or anisotropical refinement separately in each box, not
(as with <A HREF="mainreftest.html">CogenRefine</A>) for the whole
region.

<PRE>
  gen-&gt;refinementGlobal(0.2,0.1,1);
  gen-&gt;refinementIsotropicInBox(0.04,  i2);
  gen-&gt;refinementInBox(0.2,0.04,0,     i3);
  gen-&gt;refinementInBox(0.04,0.2,0,     i4);
</PRE>

 <P>There are three float parameters <i>dx, dy, dz</i> in the call of
<B>refinemenGlobal</B> and <B>refinementInBox</B>.  They define the
maximal distances between nodes in direction <i>x, y, z</i>.  The
algorithm refines the grid by bisection until the distance is below
this value.  Thus, the distances are usually smaller than <i>dx, dy,
dz</i>, but greater than half of this value.

 <P>In our two-dimensional example the value of <i>dz</i> doesn't
matter.  But we recommend to use nonetheless a reasonable (better
large) value: maybe, you later want to modify the example to create a
3D grid.


<H2>Known Bugs</H2>

 <P>For overlapping boxes, the refinement criterion remains valid also
for the hidden part.

 <P>This may be even considered as a feature ;-).

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