View source for Create a Mesh with Images and Shapes

One way to create a complicated FEA mesh, especially composite materials with complex structures of subelements, is to  define them with image and shape commands.
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== Procedure ==

An advanced method for creating FEA meshes is to create them using image and shape commands. The procedure for using this method is:

<ol>

<li>Create a standard mesh, which can be done by [[FEA Mesh Generation Commands|generating]] or [[Explicit FEA Mesh Generation|explicitly defining]] a mesh. Each area (in [[FEA Mesh Generation Commands|generated]] meshes) or element (in [[Explicit FEA Mesh Generation|explicitly defined]] meshes) can be assigned to various materials. For sections of the mesh that will be set from image or shape commands, set the material <tt>id</tt> in the [[Area Command]] to <tt>_NONE_</tt> or the <tt>mat</tt> attribute of <tt>XML</tt> commands to 0. The material will be determined later by subsequent image and shape commands.</li>

<li>Once the initial mesh is ready, use one or more interspersed [[BMPRegion Command|BMPRegion]], [[FEA Region and Hole Commands|Region, or Hole]], commands (in <tt>XML</tt> files, the corresponing commands are [[BMPRegion Command|<tt><BMP></tt>]], [[FEA Region and Hole Commands|<tt><Body></tt>, or <tt><Hole></tt>]] commands). These commands will map elements covered by the image or by shapes to the material (or hole) associated with the command. The grid can be regular or irregular. The assignment will be determined by comparing the centroid of the element to the same location in an image or to see if it is contained in a shape. To resolve complicated structures, the grid has to be fine enough to resolve material boundaries.</li>

<li>When the mesh is done, any elements initialized to <tt>_NONE_</tt> (or <tt>mat=0</tt>) but not assigned to a material by an image or shape command will automatically be removed from the mesh. This feature allows calculations on materials with voids or irregular edges without needing to use complicated [[Area Command|Area commands]] to construct the shape. If these removals cause the mesh to be partitioned into disconnected sections, however, the FEA analysis will fail. A good way to verify connectivity is to attempt to [[Resequence Command|resequence the nodes]].</li>

</ol>

== Image and Shape Commands ==

To define the mesh using a series of geometric shapes or images, the the commands are

* [[FEA Region and Hole Commands|Region Command]]: Generate elements using a series of shape commands.
* [[FEA Region and Hole Commands|Hole Command]]: Remove elements using a series of shape commands.
* [[BMPRegion Command|BMPRegion Command]]: Generate elements using a 2D image or CAD drawing of an object.

By [[Nested Shapes|nesting shapes]], you can create many more types of shapes.