surfacegrids.html

Delaunay三角形的网格剖分程序

<TITLE>COG 2.1: Surface grids</TITLE>

<H1>Surface Grids</H1>

 <P>COG 2.1 creates surface grids as for the outer boundary, as for
inner boundary faces.  These surfaces match the inner tetrahedral
grids, for inner boundaries the inner grids on above sides.

 <P>But the quality of these surface grids may be not appropriate for
boundary element methods.  The main purpose of the COG package is to
obtain good grid quality inside the regions. The surface grid is a
useful side effect, and necessary to define boundary conditions. But
to optimize its quality was not the aim of the package.

 <P>The surface points are computed as intersections with the
coordinate lines of the coordinates inside the region.  That means,
for a curved surface (here: sphere) but rectangular coordinates we
obtain a surface grid like this:

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

 <P>Note that some surface triangles have very small angles.  This may
be influenced by the <A HREF="noderemoval.html">node removal
algorithm</A>.

 <P>Another possibility is to create appropriate 
 <A HREF="mainpolartest.html">curved coordinates</A> for a surface to
obtain an appropriate, regular surface grid.