1 <!doctype HTML public "-//W3C//DTD HTML 4.0 Frameset//EN">
\r
6 <title>About meshes</title>
\r
7 <meta http-equiv="content-type" content="text/html; charset=windows-1252">
\r
8 <meta name="generator" content="RoboHelp by eHelp Corporation www.ehelp.com">
\r
9 <link rel="stylesheet" href="../default_ns.css"><script type="text/javascript" language="JavaScript" title="WebHelpSplitCss">
\r
11 if (navigator.appName !="Netscape")
\r
12 { document.write("<link rel='stylesheet' href='../default.css'>");}
\r
15 <style type="text/css">
\r
17 img_whs1 { border:none; width:30px; height:30px; float:none; border-style:none; }
\r
18 ul.whs2 { list-style:disc; }
\r
19 p.whs3 { text-indent:8px; }
\r
20 p.whs4 { text-indent:48px; }
\r
21 h4.whs5 { text-indent:1px; }
\r
22 p.whs6 { text-indent:1px; }
\r
23 img_whs7 { border:none; width:36px; height:38px; float:none; border-style:none; }
\r
24 p.whs8 { font-weight:bold; text-indent:1px; }
\r
26 </style><script type="text/javascript" language="JavaScript" title="WebHelpInlineScript">
\r
29 if (innerWidth != origWidth || innerHeight != origHeight)
\r
32 if ((parseInt(navigator.appVersion) == 4) && (navigator.appName == "Netscape")) {
\r
33 origWidth = innerWidth;
\r
34 origHeight = innerHeight;
\r
40 <style type="text/css">
\r
42 div.WebHelpPopupMenu { position:absolute; left:0px; top:0px; z-index:4; visibility:hidden; }
\r
43 p.WebHelpNavBar { text-align:right; }
\r
45 </style><script type="text/javascript" language="javascript1.2" src="../whmsg.js"></script>
\r
46 <script type="text/javascript" language="javascript" src="../whver.js"></script>
\r
47 <script type="text/javascript" language="javascript1.2" src="../whproxy.js"></script>
\r
48 <script type="text/javascript" language="javascript1.2" src="../whutils.js"></script>
\r
49 <script type="text/javascript" language="javascript1.2" src="../whtopic.js"></script>
\r
50 <script type="text/javascript" language="javascript1.2">
\r
52 if (window.gbWhTopic)
\r
54 if (window.setRelStartPage)
\r
56 addTocInfo("MESH module\nCreating meshes\nAbout meshes");
\r
57 addButton("show",BTN_IMG,"Show","","","","",0,0,"../whd_show0.gif","../whd_show2.gif","../whd_show1.gif");
\r
58 addButton("hide",BTN_IMG,"Hide","","","","",0,0,"../whd_hide0.gif","../whd_hide2.gif","../whd_hide1.gif");
\r
63 if (window.setRelStartPage)
\r
65 setRelStartPage("../index.htm");
\r
75 document.location.reload();
\r
79 <body><script type="text/javascript" language="javascript1.2">
\r
81 if (window.writeIntopicBar)
\r
85 <h1>About meshes</h1>
\r
87 <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
\r
88 a discretization of a geometrical CAD model into a set of entities with
\r
89 a simple topology. In MESH there are two options of creation of meshes,
\r
94 <ul type="disc" class="whs2">
\r
96 <li class=kadov-p><p>generate meshes on the basis of geometrical shapes
\r
97 produced in the GEOM module, </p></li>
\r
99 <li class=kadov-p><p>create your own meshes using the MESH functions
\r
100 destined for modification of generated meshes. </p></li>
\r
105 <p>The topology of a mesh is described by the relationships between its
\r
106 entities including:</p>
\r
108 <p class="whs3"> </p>
\r
110 <ul type="disc" class="whs2">
\r
112 <li class=kadov-p><p class="whs3"><span style="font-weight: bold;"><B>Node</B></span>
\r
113 \96 0D element of a mesh presented by a point with coordinates (x, y, z).</p></li>
\r
115 <li class=kadov-p><p class="whs3"><span style="font-weight: bold;"><B>Edge</B></span>
\r
116 \96 1D element of a mesh defined by two nodes.</p></li>
\r
118 <li class=kadov-p><p class="whs3"><span style="font-weight: bold;"><B>Face</B></span>
\r
119 \96 2D element of a mesh defined by three or four edges (closed contour).</p></li>
\r
121 <li class=kadov-p><p class="whs3"><span style="font-weight: bold;"><B>Volume</B></span>
\r
122 \96 3D element of a mesh defined by several faces.</p></li>
\r
125 <p class="whs3"> </p>
\r
127 <p class="whs4">These entities are considered as topological
\r
128 entities and they don't imply any geometric representation. Only <span
\r
129 style="font-weight: bold;"><B>Nodes</B></span> reference geometric
\r
130 representations of points with definite coordinates. <span style="text-indent: 8px;">The
\r
131 node entity will contain additional
\r
132 information about its position in the space and its relations with the
\r
133 meshed CAD model. Its position could be described in the following way:</span></p>
\r
135 <p class="whs4"> </p>
\r
137 <ul type="disc" class="whs2">
\r
139 <li class=kadov-p><p class="whs3"><span style="font-weight: bold;"><B>2D
\r
140 position</B></span>. It is a free position defined by only two coordinates
\r
143 <li class=kadov-p><p class="whs3"><span style="font-weight: bold;"><B>3D
\r
144 position</B></span>. It is a free position defined by three coordinates x,y
\r
147 <li class=kadov-p><p class="whs3"><span style="font-weight: bold;"><B>Surface
\r
148 position</B></span>. It characterizes the position of a node on a geometric
\r
149 surface and is defined by the u,v position in the parametric space of
\r
150 the corresponding surface.</p></li>
\r
152 <li class=kadov-p><p class="whs3"><span style="font-weight: bold;"><B>Line
\r
153 position</B></span>. It characterizes the position of a node on a geometric
\r
154 curve and is defined by the u parameter and the corresponding curve.</p></li>
\r
156 <li class=kadov-p><p class="whs3"><span style="font-weight: bold;"><B>Vertex
\r
157 position</B></span>. It characterizes the position of a node on a geometric
\r
158 point of the meshed CAD model and is defined by the x,y,z coordinates
\r
159 of the corresponding vertex.</p></li>
\r
162 <p class="whs3"> </p>
\r
164 <p class="whs3"> </p>
\r
166 <h4 class="whs5">Connections</h4>
\r
168 <p class="whs6">Each mesh entity bounds 0 or more mesh entities
\r
169 of higher dimension. In the same way each mesh entity is bounded by 0
\r
170 or more mesh entities of lower dimension:</p>
\r
172 <p class="whs6"> </p>
\r
174 <ul type="disc" class="whs2">
\r
176 <li class=kadov-p><p class="whs6">A node bounds edges,
\r
177 faces and volumes</p></li>
\r
179 <li class=kadov-p><p class="whs6">An edge bounds faces,
\r
180 and volumes</p></li>
\r
182 <li class=kadov-p><p class="whs6">A face bounds volumes</p></li>
\r
184 <li class=kadov-p><p class="whs6">A volume is bounded
\r
185 by faces, edges and nodes</p></li>
\r
187 <li class=kadov-p><p class="whs6">A face is bounded by
\r
188 edges, and nodes</p></li>
\r
190 <li class=kadov-p><p class="whs6">An edge is bounded by
\r
194 <p class="whs6"> </p>
\r
196 <p class="whs6">You can notice that there are two types of
\r
197 connections: <span style="font-weight: bold;"><B>inverse</B></span> and <span
\r
198 style="font-weight: bold;"><B>direct</B></span> connections.</p>
\r
200 <p class="whs6"> </p>
\r
202 <h4 class="whs5">Inverse connections</h4>
\r
204 <p class="whs6"> </p>
\r
206 <p class="whs6">This relationship has a particularity that
\r
207 the order of bounded entities has not a direct meaning. Also the number
\r
208 of bounded entities is not fixed.</p>
\r
210 <p class="whs6"> </p>
\r
212 <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.
\r
213 The 3rd edge has no more sense that the 5th one.</p>
\r
215 <p class="whs6"> </p>
\r
217 <p class="whs8">Direct connections</p>
\r
219 <p class="whs6"> </p>
\r
221 <p class="whs6">This relationship has a particularity that
\r
222 the order of bounding entities is meaningful. The number of bounding entities
\r
223 is fixed and depends on the type of the entity (hexahedron, tetrahedron,
\85).</p>
\r
225 <p class="whs6"> </p>
\r
227 <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
\r
228 nodes. A face is composed of 3 or 4 edges depending if we are dealing
\r
229 with triangles or quadrangles.</p>
\r
231 <p class="whs6"> </p>
\r
233 <p class="whs6">The connections are not only restricted to
\r
234 entities of one dimension higher or lower. For example some algorithms
\r
235 may be interested to retrieve all the faces surrounding a node.</p>
\r
237 <p class="whs6"> </p>
\r
239 <p class="whs6"> </p>
\r
241 <p class="whs6"> </p>
\r
243 <script type="text/javascript" language="javascript1.2">
\r
245 if (window.writeIntopicBar)
\r
246 writeIntopicBar(0);
\r