mirror of
https://git.salome-platform.org/gitpub/modules/smesh.git
synced 2024-12-27 09:50:34 +05:00
246 lines
8.3 KiB
HTML
Executable File
246 lines
8.3 KiB
HTML
Executable File
<!doctype HTML public "-//W3C//DTD HTML 4.0 Frameset//EN">
|
||
|
||
<html>
|
||
|
||
<head>
|
||
<title>About meshes</title>
|
||
<meta http-equiv="content-type" content="text/html; charset=windows-1252">
|
||
<meta name="generator" content="RoboHelp by eHelp Corporation www.ehelp.com">
|
||
<link rel="stylesheet" href="../default_ns.css"><script type="text/javascript" language="JavaScript" title="WebHelpSplitCss">
|
||
<!--
|
||
if (navigator.appName !="Netscape")
|
||
{ document.write("<link rel='stylesheet' href='../default.css'>");}
|
||
//-->
|
||
</script>
|
||
<style type="text/css">
|
||
<!--
|
||
img_whs1 { border:none; width:30px; height:30px; float:none; border-style:none; }
|
||
ul.whs2 { list-style:disc; }
|
||
p.whs3 { text-indent:8px; }
|
||
p.whs4 { text-indent:48px; }
|
||
h4.whs5 { text-indent:1px; }
|
||
p.whs6 { text-indent:1px; }
|
||
img_whs7 { border:none; width:36px; height:38px; float:none; border-style:none; }
|
||
p.whs8 { font-weight:bold; text-indent:1px; }
|
||
-->
|
||
</style><script type="text/javascript" language="JavaScript" title="WebHelpInlineScript">
|
||
<!--
|
||
function reDo() {
|
||
if (innerWidth != origWidth || innerHeight != origHeight)
|
||
location.reload();
|
||
}
|
||
if ((parseInt(navigator.appVersion) == 4) && (navigator.appName == "Netscape")) {
|
||
origWidth = innerWidth;
|
||
origHeight = innerHeight;
|
||
onresize = reDo;
|
||
}
|
||
onerror = null;
|
||
//-->
|
||
</script>
|
||
<style type="text/css">
|
||
<!--
|
||
div.WebHelpPopupMenu { position:absolute; left:0px; top:0px; z-index:4; visibility:hidden; }
|
||
-->
|
||
</style><script type="text/javascript" language="javascript1.2" src="../whmsg.js"></script>
|
||
<script type="text/javascript" language="javascript" src="../whver.js"></script>
|
||
<script type="text/javascript" language="javascript1.2" src="../whproxy.js"></script>
|
||
<script type="text/javascript" language="javascript1.2" src="../whutils.js"></script>
|
||
<script type="text/javascript" language="javascript1.2" src="../whtopic.js"></script>
|
||
</head>
|
||
<body><script type="text/javascript" language="javascript1.2">
|
||
<!--
|
||
if (window.gbWhTopic)
|
||
{
|
||
if (window.addTocInfo)
|
||
{
|
||
addTocInfo("MESH module\nCreating meshes\nAbout meshes");
|
||
addButton("show",BTN_TEXT,"Show","","","","",0,0,"","","");
|
||
|
||
}
|
||
if (window.writeBtnStyle)
|
||
writeBtnStyle();
|
||
|
||
if (window.writeIntopicBar)
|
||
writeIntopicBar(1);
|
||
|
||
if (window.setRelStartPage)
|
||
{
|
||
setRelStartPage("../smesh.htm");
|
||
|
||
autoSync(1);
|
||
sendSyncInfo();
|
||
sendAveInfoOut();
|
||
}
|
||
}
|
||
else
|
||
if (window.gbIE4)
|
||
document.location.reload();
|
||
//-->
|
||
</script>
|
||
<h1>About meshes</h1>
|
||
|
||
<p><img src="../i_blue.jpg" x-maintain-ratio="TRUE" width="30px" height="30px" border="0" class="img_whs1"> <span style="font-weight: bold;"><B>MESH</B></span> represents
|
||
a discretization of a geometrical CAD model into a set of entities with
|
||
a simple topology. In MESH there are two options of creation of meshes,
|
||
you can:</p>
|
||
|
||
<p> </p>
|
||
|
||
<ul type="disc" class="whs2">
|
||
|
||
<li class=kadov-p><p>generate meshes on the basis of geometrical shapes
|
||
produced in the GEOM module, </p></li>
|
||
|
||
<li class=kadov-p><p>create your own meshes using the MESH functions
|
||
destined for modification of generated meshes. </p></li>
|
||
</ul>
|
||
|
||
<p> </p>
|
||
|
||
<p>The topology of a mesh is described by the relationships between its
|
||
entities including:</p>
|
||
|
||
<p class="whs3"> </p>
|
||
|
||
<ul type="disc" class="whs2">
|
||
|
||
<li class=kadov-p><p class="whs3"><span style="font-weight: bold;"><B>Node</B></span>
|
||
<20> 0D element of a mesh presented by a point with coordinates (x, y, z).</p></li>
|
||
|
||
<li class=kadov-p><p class="whs3"><span style="font-weight: bold;"><B>Edge</B></span>
|
||
<20> 1D element of a mesh defined by two nodes.</p></li>
|
||
|
||
<li class=kadov-p><p class="whs3"><span style="font-weight: bold;"><B>Face</B></span>
|
||
<20> 2D element of a mesh defined by three or four edges (closed contour).</p></li>
|
||
|
||
<li class=kadov-p><p class="whs3"><span style="font-weight: bold;"><B>Volume</B></span>
|
||
<20> 3D element of a mesh defined by several faces.</p></li>
|
||
</ul>
|
||
|
||
<p class="whs3"> </p>
|
||
|
||
<p class="whs4">These entities are considered as topological
|
||
entities and they don't imply any geometric representation. Only <span
|
||
style="font-weight: bold;"><B>Nodes</B></span> reference geometric
|
||
representations of points with definite coordinates. <span style="text-indent: 8px;">The
|
||
node entity will contain additional
|
||
information about its position in the space and its relations with the
|
||
meshed CAD model. Its position could be described in the following way:</span></p>
|
||
|
||
<p class="whs4"> </p>
|
||
|
||
<ul type="disc" class="whs2">
|
||
|
||
<li class=kadov-p><p class="whs3"><span style="font-weight: bold;"><B>2D
|
||
position</B></span>. It is a free position defined by only two coordinates
|
||
x,y.</p></li>
|
||
|
||
<li class=kadov-p><p class="whs3"><span style="font-weight: bold;"><B>3D
|
||
position</B></span>. It is a free position defined by three coordinates x,y
|
||
and z.</p></li>
|
||
|
||
<li class=kadov-p><p class="whs3"><span style="font-weight: bold;"><B>Surface
|
||
position</B></span>. It characterizes the position of a node on a geometric
|
||
surface and is defined by the u,v position in the parametric space of
|
||
the corresponding surface.</p></li>
|
||
|
||
<li class=kadov-p><p class="whs3"><span style="font-weight: bold;"><B>Line
|
||
position</B></span>. It characterizes the position of a node on a geometric
|
||
curve and is defined by the u parameter and the corresponding curve.</p></li>
|
||
|
||
<li class=kadov-p><p class="whs3"><span style="font-weight: bold;"><B>Vertex
|
||
position</B></span>. It characterizes the position of a node on a geometric
|
||
point of the meshed CAD model and is defined by the x,y,z coordinates
|
||
of the corresponding vertex.</p></li>
|
||
</ul>
|
||
|
||
<p class="whs3"> </p>
|
||
|
||
<p class="whs3"> </p>
|
||
|
||
<h4 class="whs5">Connections</h4>
|
||
|
||
<p class="whs6">Each mesh entity bounds 0 or more mesh entities
|
||
of higher dimension. In the same way each mesh entity is bounded by 0
|
||
or more mesh entities of lower dimension:</p>
|
||
|
||
<p class="whs6"> </p>
|
||
|
||
<ul type="disc" class="whs2">
|
||
|
||
<li class=kadov-p><p class="whs6">A node bounds edges,
|
||
faces and volumes</p></li>
|
||
|
||
<li class=kadov-p><p class="whs6">An edge bounds faces,
|
||
and volumes</p></li>
|
||
|
||
<li class=kadov-p><p class="whs6">A face bounds volumes</p></li>
|
||
|
||
<li class=kadov-p><p class="whs6">A volume is bounded
|
||
by faces, edges and nodes</p></li>
|
||
|
||
<li class=kadov-p><p class="whs6">A face is bounded by
|
||
edges, and nodes</p></li>
|
||
|
||
<li class=kadov-p><p class="whs6">An edge is bounded by
|
||
nodes</p></li>
|
||
</ul>
|
||
|
||
<p class="whs6"> </p>
|
||
|
||
<p class="whs6">You can notice that there are two types of
|
||
connections: <span style="font-weight: bold;"><B>inverse</B></span> and <span
|
||
style="font-weight: bold;"><B>direct</B></span> connections.</p>
|
||
|
||
<p class="whs6"> </p>
|
||
|
||
<h4 class="whs5">Inverse connections</h4>
|
||
|
||
<p class="whs6"> </p>
|
||
|
||
<p class="whs6">This relationship has a particularity that
|
||
the order of bounded entities has not a direct meaning. Also the number
|
||
of bounded entities is not fixed.</p>
|
||
|
||
<p class="whs6"> </p>
|
||
|
||
<p class="whs6"><img src="../pics/exemple.gif" x-maintain-ratio="TRUE" width="36px" height="38px" border="0" class="img_whs7"> The edges surrounding a node.
|
||
The 3rd edge has no more sense that the 5th one.</p>
|
||
|
||
<p class="whs6"> </p>
|
||
|
||
<p class="whs8">Direct connections</p>
|
||
|
||
<p class="whs6"> </p>
|
||
|
||
<p class="whs6">This relationship has a particularity that
|
||
the order of bounding entities is meaningful. The number of bounding entities
|
||
is fixed and depends on the type of the entity (hexahedron, tetrahedron,<2C>).</p>
|
||
|
||
<p class="whs6"> </p>
|
||
|
||
<p class="whs6"><img src="../pics/exemple.gif" x-maintain-ratio="TRUE" width="36px" height="38px" border="0" class="img_whs7"> An edge is composed of two
|
||
nodes. A face is composed of 3 or 4 edges depending if we are dealing
|
||
with triangles or quadrangles.</p>
|
||
|
||
<p class="whs6"> </p>
|
||
|
||
<p class="whs6">The connections are not only restricted to
|
||
entities of one dimension higher or lower. For example some algorithms
|
||
may be interested to retrieve all the faces surrounding a node.</p>
|
||
|
||
<p class="whs6"> </p>
|
||
|
||
<p class="whs6"> </p>
|
||
|
||
<p class="whs6"> </p>
|
||
|
||
<script type="text/javascript" language="javascript1.2">
|
||
<!--
|
||
if (window.writeIntopicBar)
|
||
writeIntopicBar(0);
|
||
//-->
|
||
</script>
|
||
</body>
|
||
</html>
|