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documentation/lagrit_manual/commands/intersect_elements.txt

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+.. _intersect_elements:
+
+**_INTERSECT_ELEMENTS_**
+
+> This command takes two meshes and creates an element-based attribute in
+mesh1 that contains the number of elements in mesh2 that intersected the
+respective element in mesh1.
+
+>
+
+> We define intersection as two elements sharing any common point.
+
+FORMAT:
+
+> **intersect_elements** / mesh1 / mesh2 / [attrib_name]
+
+NOTES:
+
+> [attrib_name] specifies the name of the element based attribute in mesh1
+that is created by this command. The default name for this attribute is
+in_<mesh2>. For example, if the comand syntax was:
+
+>
+
+>> **intersect_elements**/cmo_strat/cmo_well/
+
+>
+
+> the element based attribute that stores the number of intersections would be
+named in_cmo_well. It is worth noting that GMV does not take kindly to names
+that are longer than eight characters and will truncate them without even
+thinking twice, resulting in the name used in our example being changed to
+in_cmo_w. Therefore, it is good practice to use your own attribute names less
+than eight characters if possible.
+
+>
+
+> This code has been slightly modified to work with AMR grids produced in X3D.
+This modification depends on an element based attribute that X3D creates
+called **itetkid**. If this attribute is not present, **intersect_elements**
+will **NOT** be able to recognize the AMR grid, and will intersect all
+elements of the octree. With the itetkid attribute present, only leaves of the
+octree which intersect will be flagged.
+
+>
+
+> **intersect_elements** is not designed to work with every element-element
+combination, but it is pretty thorough. The following table shows what
+element/element intersetion capabilities are available. An **X** in the box
+means that the intersection is supported.
+
+>
+
+> &nbsp_place_holder;
+
+> point
+
+> line
+
+> tri
+
+> quad
+
+> tet
+
+> pyr
+
+> hex
+
+>
+
+> point
+
+> **X**
+
+> **X**
+
+> **X**
+
+> **X**
+
+> **X**
+
+> **X**
+
+> **X**
+
+>
+
+> line
+
+> **X**
+
+> **X**
+
+> **X**
+
+> **X**
+
+> **X**
+
+> &nbsp_place_holder;
+
+> **X**
+
+>
+
+> tri
+
+> **X**
+
+> **X**
+
+> **X**
+
+> **X**
+
+> **X**
+
+> &nbsp_place_holder;
+
+> **X**
+
+>
+
+> quad
+
+> **X**
+
+> **X**
+
+> **X**
+
+> **X**
+
+> **X**
+
+> &nbsp_place_holder;
+
+> **X**
+
+>
+
+> tet
+
+> **X**
+
+> **X**
+
+> **X**
+
+> **X**
+
+> **X**
+
+> &nbsp_place_holder;
+
+> **X**
+
+>
+
+> pyr
+
+> **X**
+
+> &nbsp_place_holder;
+
+> &nbsp_place_holder;
+
+> &nbsp_place_holder;
+
+> &nbsp_place_holder;
+
+> &nbsp_place_holder;
+
+> &nbsp_place_holder;
+
+>
+
+> hex
+
+> **X**
+
+> **X**
+
+> **X**
+
+> **X**
+
+> **X**
+
+> &nbsp_place_holder;
+
+> **X**
+
+>
+
+> For example, this means that if you have a mesh that has hexes and tets in
+it, you could intersect it with a mesh that has anything but pyramids in it.
+
+>
+
+> Finally, **intersect_elements** is based on a k-D-R tree implementation to
+improve performance in many circumstances. Unfortunately, there is no way to
+improve performance if the elements being intersected have many candidate
+elements in their bounding boxes. As such, there are situations where running
+time may be improved by refining mesh2 such that its elements are of
+comparable size with those of mesh1.
+
+EXAMPLES:
+
+> **intersect_elements**/cmo_grid/cmo_sphere/
+
+>
+
+> **intersect_elements**/cmo_grid/cmo_well/obswell
+