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documentation/lagrit_manual/commands/extrude.txt

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+.. _extrude:
+
+> &nbsp_place_holder;
+
+>
+
+> **_EXTRUDE_**
+
+> > This command takes a topologically 1d or 2d mesh (a line, a set of line
+segments, or a planar or non-planar surface) and extrudes it into three
+dimensions along either the normal to the curve or surface (default), along a
+user defined vector, or to a set of points that the user has specified.
+
+> > If the extrusion was along the normal of the surface or along a user
+defined vector, the command can optionally find the external surface of the
+volume created and return that to the user.
+
+>
+
+> FORMAT:
+
+>
+
+>> **extrude**/mesh1/mesh2/**const|min**/offset/**volume|bubble**/[**norm**|x1
+,y1,z1]
+
+> > OR
+
+> > **extrude**/mesh1/mesh2/**interp**/layers/**range1/range2**
+
+> > where** range1 **and** range2 **are defined as
+**[pset,get,**`pset_name`**|**`ifirst,ilast,istride`**]**
+
+>
+
+> mesh1 is the name of the resulting mesh.
+
+>
+
+> mesh2 is the name of the initial mesh. This mesh must be made up of **lines,
+tris, quads, or hybrids**.
+
+>
+
+> **const** is a keyword that indicates that the distance from each of the
+points in the initial mesh along the extruding vector will be equal to
+offset.Therefore, if you wanted the extruded mesh to have the same surface or
+edge characteristics as the original mesh on both the initial and newly formed
+surface or edge, you would use **const**.
+
+>
+
+> **min** is a keyword and indicates that the minimum distance along the
+extruding vector to a reference plane that is perpendicular to the extruding
+vector will be equal to offset. This means that if you want an extruded mesh
+with at least one flat side, you would use **min**. This also means that if
+you use **min**, extrude computes the "bottom point" on the initial mesh, or
+the point closest to the reference plane, and then extrudes that point by min,
+all the other points will therefore be extruded by a larger distance. This
+avoids the problem of having the initial mesh intersect the reference plane
+that forms the "bottom" of the created mesh.
+
+>
+
+> **interp** is a keyword and indicates a different kind of extrusion. Instead
+of giving the initial mesh a direction in which to be extruded, this keyword
+specifies that the initial mesh is made up of two sets of points to be
+connected. These point sets are defined by **range1** and **range2**. The
+ranges can be defined using the standard LaGriT techniques of **pset**,
+**get**, <pset name> or ifirst, ilast, istride.
+
+>
+
+> layers is the number of layers of elements that will be placed between the
+original two surfaces. This is a good point distribution technique. The final
+number of layers of points will be equal to layers+1. It must be an integer.
+
+>
+
+> offset is the length of extrusion. It can either be an integer or a real.
+
+>
+
+> **volume** is a keyword and indicates that the volume that was extruded is
+to be returned to the user (i.e., the operation will result in either a
+topologically 2d (quad) mesh if the initial mesh was topologically 1d, or a
+topologically 3d (prism or hex) mesh if the initial mesh was topologically
+2d). **bubble** is a keyword and indicates that the external surface of the
+volume created will be returned. If bubble is used, hextotet will be called on
+the final surface, as well as extract.
+
+>
+
+> The final argument is optional. It must either be the keyword **norm**, or a
+three valued vector (in cartesian space) specifying a direction. The default,
+if no argument is provided, is **norm**. If **norm** is chosen, the element
+area weighted normal to the surface or curve is computed, and the initial mesh
+is extruded in that direction. Otherwise, if a vector value is specified, the
+vector is normalized, and its direction used to extrude the initial mesh.
+
+>
+
+> NOTES:
+
+>
+
+>> This code works on meshes containing lines, quads, triangles, or hybrid
+polygons. If there are lines in the initial mesh, they become quads; tris
+become prisms; and quads become hexes. If bubble is used, however, lines are
+not permitted because they do not result in a mesh that extract and hextotet
+agree with. The code will error out in this situation.
+
+> > It is very possible to create an invalid mesh object with this command,
+especially if the initial mesh is a multivalued surface, or if the extruding
+vector is in a direction parallel to the plane the initial surface is in. You
+have been warned.
+
+> > If the **interp** keyword is used, the code expects the number of points
+in **range1** and **range2** to be equal, and to correspond such that the
+first point in **range1** will connect to the first point in **range2 **in the
+final mesh object, etc. Other setups will result in a twisted, perhaps invalid
+mesh object.
+
+>
+
+> EXAMPLES:
+
+>
+
+>> **extrude**/cmo_hex/cmo_quad/**const**/5.0/**volume**
+
+> > This would result in hexes being created out of the initial quad sheet.
+First, since **const** and **volume** are used, the quad sheet will be
+extruded a constant amount from each point. Second, since the extruding vector
+and **norm** are omitted, the extrusion will occur on the average normal to
+the plane. Therefore, this command will result in a mesh of hexahedrons
+extruded 5.0 units in an orthogonal direction. (Or, more succinctly, a mesh of
+parallelopipeds of height 5.)
+
+> > **extrude**/cmo_prism/cmo_tri/**min**/10/**volume**/1,2,-1
+
+> > This command would result in prisms being created out of the initial tri
+sheet. First, since **min** is used, the "bottom" of the extruded volume would
+be a plane. Second, because the vector 1, 2, -1 is specified, the extrusion
+will be in that direction (again the magnitude is not important, the vector is
+normalized to a unit vector), not in the direction of the average normal.
+
+> > **extrude**/cmo_bigbox/cmo_quad/**const**/5.0/**bubble/**
+
+> > This would result in a surface surrounding an amalgamation of
+parallelopipeds created from the initial quad sheet. First, since **const** is
+used the quads will be extruded a constant amount from each point in the quad
+sheet. Second, since the extruding vector and **norm** are omitted, the
+extrusion will occur on the average normal to the plane. Therefore, this
+command will result in a mesh of tris that form the surface of a group of
+parallelopipeds extruded 5.0 units in an orthogonal direction.
+
+> > **extrude**/cmo_arbshape/cmo_tri/**min**/7.5/**bubble**/3,-2.5,-6
+
+> > This command would result in a mesh of tris that form a surface enclosing
+a volume of prisms being created out of the initial tri sheet. First, since
+**min** is used, the "bottom" of the surface would be a plane. Second, because
+the vector 3, -2.5, -6 is specified, the extrusion will be in that direction
+(again the magnitude is not important, the vector is normalized to a unit
+vector), not in the direction of the average normal of the initial tri
+surface.
+
+> > **extrude**/cmo_prism/cmo_tris/**interp**/14/**pset, get, **bottom**/pset,
+get, **top
+
+> > This command would result in a mesh of prisms being created out of the two
+sets of tri sheets in cmo_tris as well as 14-1 layers of additional tris that
+would be interpolated. First, since interp is used, the pset defined by bottom
+would end up connected to the pset defined by top. Second, there would be 14
+layers of elements that would be placed between the psets top and bottom, so
+that the resulting grid would have 15 layers of points that would be connected
+to one another to form prisms.
+