smesh/doc/salome/gui/SMESH/input/projection_algos.doc

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\page projection_algos_page Projection Algorithms

\n Projection algorithms allow to define the mesh of a geometrical
object by the projection of another already meshed geometrical object.

<b>Projection 1D</b> algorithm allows to define the mesh of an edge
(or group of edges)
by the projection of another already meshed edge (or group of edges).
\n To apply this algorithm select the edge to be meshed (indicated in
the field \b Geometry of <b>Create mesh</b> dialog box),
<b>Projection1D</b> in the list of 1D algorithms and click the
<em>"Add Hypothesis"</em> button.
The following dialog box will appear:

\image html projection_1d.png

In this menu you can define the \b Name of the algorithm, the already
meshed source \b Edge and the \b Mesh  (It can be omitted only when 
projecting a submesh on another one from the same global Mesh). 
It could also be necessary to define the orientation of edges, 
which is done by indicating the <b>Source Vertex</b> being the first point 
of the Source Edge and the <b>Target Vertex</b> being the first point of 
the created \b Edge. 
<br>
For a group of edges, <b>Source</b> and <b>Target</b> vertices should be
shared by one edge of the group. If <b>Source</b> and <b>Target</b>
vertices are specified, the elements of the group must be adjacent.
The source and target groups must contain equal number of edges
and they must form topologically equal structures.

\n <b>Projection 2D</b> algorithm allows to define the mesh of a face
(or group of faces) by the
projection of another already meshed face (or group of faces). This
algorithm works only
if all edges of the target face have been meshed as 1D Projections of
the edges of the source face.

To apply this algorithm select the face to be meshed (indicated in the
field \b Geometry of <b>Create mesh</b> dialog box), <b>Projection
2D</b> in the list
of 2D algorithms and click the <em>"Add Hypothesis"</em> button. The
following dialog box will appear:

\image html projection_2d.png

In this menu you can define the \b Name of the algorithm, the already
meshed source \b Face and the \b Mesh (It can be omitted only when 
projecting a submesh on another one from the same global Mesh). 
It could also be necessary to define the orientation of mesh on the
face, which is done by indicating two <b>Source Vertices</b>, which
belong to the same edge of the source face, and two <b>Target
Vertices</b>, which belong to the same edge of the created \b Face.
For groups of face, they must contain equal number of faces
and they must form topologically equal structures.

\n <b>Projection 1D-2D</b> algorithm differs from <b>Projection 2D</b>
algorithm in one aspect: it generates mesh segments on edges of
the face according to the projected 2D elements; thus it does not
require the edges to be meshed by any other 1D algorithm; moreover it
does not allow to mesh edges of the face using another algorithm via
definition of sub-meshes.

\n <b>Projection 3D</b> algorithm allows to define the mesh of a shape by
the projection of another already meshed shape.  This algorithm works
only if all faces and edges of the target shape have been meshed as 1D-2D
Projections of the faces and edges of the source shape. Another
limitation is that this algorithm currently works only on boxes.

To apply this algorithm select the solid to be meshed (indicated in
the field \b Geometry of <b>Create mesh</b> dialog box), <b>Projection
3D</b> in the list of 3D algorithms and click the  button. The
following dialog box will appear:

\image html projection_3d.png

In this menu you can define the \b Name of the algorithm, the already
meshed source <b>3D shape</b> and the \b Mesh (It can be omitted only when 
projecting a submesh on another one from the same global Mesh). 
It could also be necessary to define the orientation of mesh on the shape, which is
done by indicating two <b>Source Vertices</b>, which belong to the same edge
of the source <b>3D Shape</b>, and two <b>Target Vertices</b>, which belong to the
same edge of the source <b>3D Shape</b>.

<br><b>See Also</b> a sample TUI Script of a 
\ref tui_projection "Projection Algorithms".

*/