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192 lines
6.7 KiB
Plaintext
192 lines
6.7 KiB
Plaintext
/*!
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\page pattern_mapping_page Pattern mapping
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<br><h2>About patterns</h2>
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The pattern describes a mesh to generate: positions of nodes within a
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geometrical domain and nodal connectivity of elements. As well, a
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pattern specifies the so-called key-points, i.e. nodes that will be
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located at geometrical vertices. Pattern description is stored in
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\<pattern_name\>.smp file.
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The smp file contains 4 sections:
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-# The first line holds the total number of the pattern nodes (N).
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-# The next N lines describe nodes coordinates. Each line holds 2
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coordinates of a node for 2D pattern or 3 cordinates for 3D pattern.
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Note, that for 3D pattern only relateive values in range [0;1] are
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valid for coordinates of the nodes.
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-# A key-points line: indices of nodes to be mapped on geometrical
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vertices (for 2D pattern only). An index n refers to a node described
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on an n-th line of section 2. The first node index is zero. For 3D
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pattern key points are not specified.
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-# The rest lines describe nodal connectivity of elements, one line
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for an element. A line holds indices of nodes forming an element. An
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index n refers to a node described on an n-th line of the section
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2. The first node index is zero. There must be 3 or 4 indices on a
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line for 2D pattern (only 2d elements are allowed) and 4, 5, 6 or 8
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indices for 3D pattern (only 3d elements are allowed).
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The 2D pattern must contain at least one element and at least one
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key-point. All key-points must lay on boundaries.
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The 3D pattern must contain at least one element.
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An example of a simple 2D pattern smp file:
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\code
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!!! SALOME 2D mesh pattern file
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!!!
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!!! Nb of points:
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9
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200 0 !- 0
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100 0 !- 1
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0 0 !- 2
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0 -100 !- 3
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0 -200 !- 4
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100 -200 !- 5
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200 -200 !- 6
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200 -100 !- 7
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100 -100 !- 8
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!!! Indices of 4 key-points
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2 0 4 6
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!!! Indices of points of 6 elements
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0 1 8
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8 5 6 7
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2 3 8
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8 3 4 5
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8 7 0
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8 1 2
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\endcode
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The image below provides a preview of above described pattern:
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\image html pattern2d.png
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An example of a simple 3D pattern smp file:
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\code
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!!! SALOME 3D mesh pattern file
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!!!
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!!! Nb of points:
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9
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0 0 0 !- 0
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1 0 0 !- 1
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0 1 0 !- 2
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1 1 0 !- 3
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0 0 1 !- 4
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1 0 1 !- 5
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0 1 1 !- 6
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1 1 1 !- 7
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0.5 0.5 0.5 !- 8
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!!! Indices of points of 6 elements:
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0 1 5 4 8
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7 5 1 3 8
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3 2 6 7 8
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2 0 4 6 8
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0 2 3 1 8
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4 5 7 6 8
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\endcode
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<br><h2>Application of pattern mapping</h2>
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<em>To apply pattern mapping to a geometrical object:</em>
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From the \b Modification menu choose the <b>Pattern Mapping</b> item or click
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<em>"Pattern mapping"</em> button in the toolbar.
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\image html image98.png
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<center><em>"Pattern mapping" button</em></center>
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The following dialog box shall appear:
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\image html patternmapping1.png
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<center><b> 2D Pattern Mapping dialog box</b></center>
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\image html patternmapping2.png
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<center><b> 3D Pattern Mapping dialog box</b></center>
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To apply a pattern to a geometrical object, you should specify:
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-# For 2D pattern
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- A face having the number of vertices equal to the number of
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key-points in the pattern; the number of key-points on internal
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boundaries of a pattern must also be equal to the number of vertices
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on internal boundaries of a face;
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- A vertex to which the first key-point should be mapped;
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- Reverse or not the order of key-points. (The order of vertices of
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a face is counterclockwise looking from outside).
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-# For 3D pattern
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- 3D block (Solid) object;
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- Two vertices that specify the order of nodes in the resulting
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mesh.
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Then you either load a .smp pattern file previously created manually
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by clicking on the <em>"Load pattern"</em> button, or click on the \b
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New button for automatic generation of the pattern.
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For an automatic generation you just specify a geometrical face (for
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2D) or solid (for 3d) having a mesh built on it. Mesh nodes lying on
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face vertices become key-points of 2D pattern. Additionally, for 2D
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pattern you may choose the way of getting nodes coordinates by
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<b>projecting nodes on the face</b> instead of using
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"positions on face" generated by mesher (if there is any). Faces
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having a seam edge can't be used for automatic pattern creation.
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When creating a pattern from an existing mesh, there are two possible
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cases:
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- A sub-mesh on face/solid is selected. A pattern is created from the 2d/3d
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elements bound to a face/solid by mesher. For 2D pattern, node coordinates are either
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"positions on face" computed by mesher, or coordinates got by node
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projection on a geometrical surface, according to the user choice. For
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3D pattern, nodes coordinates correspond to the nodes computed by mesher.
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- A mesh where the main shape is a face/solid, is selected. A pattern is
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created from all the 2d/3d elements in a mesh. In addition, for 2D
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pattern, if all mesh elements are build by mesher, the user can select
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the way of getting nodes coordinates, else all nodes are projected on
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a face surface.
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\image html a-patterntype.png
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<center><b> 2D Pattern Creation dialog box</b></center>
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\image html a-patterntype1.png
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<center><b> 3D Pattern Creation dialog box</b></center>
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<br><h2>Mapping algorithm</h2>
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The mapping algorithm for 2D case is as follows:
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- Key-points are set in the order that they are encountered when
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walking along a pattern boundary so that elements are on the left. The
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first key-point is preserved.
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- Find geometrical vertices corresponding to key-points by vertices
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order in a face boundary; here, "Reverse order of key-points" flag is
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taken into account. \image html image95.gif
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- Boundary nodes of a pattern are mapped onto edges of a face: a
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node located between certain key-points on a pattern boundary is
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mapped on a geometrical edge limited by corresponding geometrical
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vertices. Node position on an edge reflects its distance from two
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key-points. \image html image96.gif
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- Coordinates of a non-boundary node in a parametric space of a face
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are defined as following. In a parametric space of a pattern, a node
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lays at the intersection of two iso-lines, each of which intersects a
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pattern boundary at least at two points. Knowing mapped positions of
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boundary nodes, we find where isoline-boundary intersection points are
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mapped to, and hence we can find mapped isolines direction and then,
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two node positions on two mapped isolines. The eventual mapped
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position of a node is found as an average of positions on mapped
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isolines. \image html image97.gif
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For 3D case the algorithm is similar.
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<b>See Also</b> a sample TUI Script of a
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\ref tui_pattern_mapping "Pattern Mapping" operation.
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*/
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