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87 lines
3.3 KiB
Plaintext
87 lines
3.3 KiB
Plaintext
/*!
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\page about_meshes_page About meshes
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\n \b MESH represents a discretization of a geometrical CAD model into
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a set of entities with a simple topology. In MESH there are two
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options of creation of meshes, you can:
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<ul>
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<li>generate meshes on the basis of geometrical shapes produced in the GEOM module,</li>
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<li>create your own meshes using the MESH functions destined for modification of generated meshes.</li>
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</ul>
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The topology of a mesh is described by the relationships between its
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entities including:
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<ul>
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<li>\b Node — 0D object of a mesh presented by a point with coordinates (x, y, z).</li>
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<li>\b Edge — 1D element of a mesh defined by two nodes.</li>
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<li>\b Face — 2D element of a mesh defined by three or four edges (closed contour).</li>
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<li>\b Volume — 3D element of a mesh defined by several faces.</li>
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</ul>
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These entities are
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considered as topological entities and they don't
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imply any geometric representation. Only \b Nodes reference geometric
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representations of points with definite coordinates. The node entity
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will contain additional information about its position in the space
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and its relations with the meshed CAD model. Its position could be
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described in the following way:
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<ul>
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<li><b>2D position</b>. It is a free position defined by only two coordinates x,y.</li>
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<li><b>3D position</b>. It is a free position defined by three coordinates x,y and z. </li>
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<li><b>Surface position</b>. It characterizes the position of a node on a
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geometric surface and is defined by the u,v position in the parametric
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space of the corresponding surface.</li>
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<li><b>Line position</b>. It characterizes the position of a node on a
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geometric curve and is defined by the u parameter and the
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corresponding curve.</li>
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<li><b>Vertex position</b>. It characterizes the position of a node on a
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geometric point of the meshed CAD model and is defined by the x,y,z
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coordinates of the corresponding vertex.</li>
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</ul>
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<br><h2>Connections</h2>
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Each mesh entity bounds 0 or more mesh entities of higher
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dimension. In the same way each mesh entity is bounded by 0 or more
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mesh entities of lower dimension:
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<ul>
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<li>A node bounds edges, faces and volumes</li>
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<li>An edge bounds faces, and volumes</li>
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<li>A face bounds volumes</li>
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<li>A volume is bounded by faces, edges and nodes</li>
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<li>A face is bounded by edges, and nodes</li>
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<li>An edge is bounded by nodes</li>
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</ul>
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You can notice that there are two types of connections: \b inverse and
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\b direct connections.
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<br><h2>Inverse connections</h2>
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This relationship has a particularity that the order of bounded
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entities has not a direct meaning. Also the number of bounded entities
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is not fixed.
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\b Example: The edges surrounding a node. The 3rd edge has no more
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sense that the 5th one.
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<br><h2>Direct connections</h2>
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This relationship has a particularity that the order of bounding
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entities is meaningful. The number of bounding entities is fixed and
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depends on the type of the entity (hexahedron, tetrahedron,?).
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\b Example: An edge is composed of two nodes. A face is composed of 3
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or 4 edges depending if we are dealing with triangles or quadrangles.
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The connections are not only restricted to entities of one dimension
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higher or lower. For example some algorithms may be interested to
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retrieve all the faces surrounding a node.
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*/
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