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1D Meshing Hypotheses



Arithmetic 1D hypothesis

Arithmetic 1D hypothesis allows to split edges into segments with a length that changes in arithmetic progression (Lk = Lk-1 + d) beginning from a given starting length and up to a given end length.

The direction of the splitting is defined by the orientation of the underlying geometrical edge. "Reverse Edges" list box allows to specify the edges for which the splitting should be made in the direction opposing to their orientation. This list box is enabled only if the geometry object is selected for the meshing. In this case the user can select edges to be reversed either directly picking them in the 3D viewer or by selecting the edges or groups of edges in the Object browser.

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Arithmetic 1D hypothesis - the size of mesh elements gradually increases

See Also a sample TUI Script of a Defining Arithmetic 1D hypothesis operation.


Deflection 1D hypothesis

Deflection 1D hypothesis can be applied for meshing curvilinear edges composing your geometrical object. It uses only one parameter: the value of deflection.
A geometrical edge is divided into equal segments. The maximum distance between a point on the edge within a segment and the line connecting the ends of the segment should not exceed the specified value of deflection . Then mesh nodes are constructed at end segment locations and 1D mesh elements are constructed on segments.

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Deflection 1D hypothesis - useful for meshing curvilinear edges

See Also a sample TUI Script of a Defining Deflection 1D hypothesis operation.


Average Length hypothesis

Average Length hypothesis can be applied for meshing of edges composing your geometrical object. Definition of this hypothesis consists of setting the length of segments, which will split these edges, and the precision of rounding. The points on the edges generated by these segments will represent nodes of your mesh. Later these nodes will be used for meshing of the faces abutting to these edges.

The precision parameter is used to allow rounding a number of segments, calculated from the edge length and average length of segment, to the lower integer, if this value outstands from it in bounds of the precision. Otherwise, the number of segments is rounded to the higher integer. Use value 0.5 to provide rounding to the nearest integer, 1.0 for the lower integer, 0.0 for the higher integer. Default value is 1e-07.

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Average length hypothesis - all 1D mesh elements are roughly equal

See Also a sample TUI Script of a Defining Average Length hypothesis operation.


Max Size

Max Size hypothesis allows splitting geometrical edges into segments not longer than the given length. Definition of this hypothesis consists of setting the maximal allowed length of segments. Use preestimated length check box lets you specify length automatically calculated basing on size of your geometrical object, namely as diagonal of bounding box divided by ten. The divider can be changed via "Ratio Bounding Box Diagonal / Max Size" preference parameter. Use preestimated length check box is enabled only if the geometrical object has been selected before hypothesis definition.

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Number of segments hypothesis

Number of segments hypothesis can be applied for meshing of edges composing your geometrical object. Definition of this hypothesis consists of setting the number of segments, which will split these edges. In other words your edges will be split into a definite number of segments with approximately the same length. The points on the edges generated by these segments will represent nodes of your mesh. Later these nodes will be used for meshing of the faces abutting to these edges.

The direction of the splitting is defined by the orientation of the underlying geometrical edge. "Reverse Edges" list box allows to specify the edges for which the splitting should be made in the direction opposing to their orientation. This list box is enabled only if the geometry object is selected for the meshing. In this case the user can select edges to be reversed either directly picking them in the 3D viewer or by selecting the edges or groups of edges in the Object browser.

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You can set the type of distribution for this hypothesis in the Hypothesis Construction dialog bog :

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Equidistant Distribution - all segments will have the same length, you define only the Number of Segments.


Scale Distribution - length of segments gradually changes depending on the Scale Factor, which is a ratio of the first segment length to the last segment length.

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Distribution with Table Density - you input a number of pairs t - F(t), where t ranges from 0 to 1, and the module computes the formula, which will rule the change of length of segments and shows the curve in the plot. You can select the Conversion mode from Exponent and Cut negative.

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Distribution with Analytic Density - you input the formula, which will rule the change of length of segments and the module shows the curve in the plot.

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See Also a sample TUI Script of a Defining Number of Segments hypothesis operation.


Start and End Length hypothesis

Start and End Length hypothesis allows to divide a geometrical edge into segments so that the first and the last segments have a specified length. The length medium segments changes with automatically chosen geometric progression. Then mesh nodes are constructed at segment ends location and 1D mesh elements are constructed on them.

The direction of the splitting is defined by the orientation of the underlying geometrical edge. "Reverse Edges" list box allows to specify the edges for which the splitting should be made in the direction opposing to their orientation. This list box is enabled only if the geometry object is selected for the meshing. In this case the user can select edges to be reversed either directly picking them in the 3D viewer or by selecting the edges or groups of edges in the Object browser.

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The lengths of the first and the last segment are strictly defined

See Also a sample TUI Script of a Defining Start and End Length hypothesis operation.


Automatic Length

This hypothesis is automatically applied when you select Assign a set of hypotheses option in Create Mesh menu.

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The dialog box prompts you to define the quality of the future mesh by only one parameter, which is Fineness, ranging from 0 (coarse mesh, low number of elements) to 1 (extremely fine mesh, great number of elements). Compare one and the same object (sphere) meshed with minimum and maximum value of this parameter.

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Example of a very rough mesh. Automatic Length works for 0.

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Example of a very fine mesh. Automatic Length works for 1.


Fixed points 1D hypothesis

Fixed points 1D hypothesis allows splitting edges through a set of points parameterized on the edge (from 1 to 0) and a number of segments for each interval limited by the points.

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It is possible to check in Same Nb. Segments for all intervals option and to define one value for all intervals.

The splitting direction is defined by the orientation of the underlying geometrical edge. "Reverse Edges" list box allows to specify the edges for which the splitting should be made in the direction opposite to their orientation. This list box is enabled only if the geometrical object is selected for meshing. In this case it is possible to select the edges to be reversed either directly picking them in the 3D viewer or selecting the edges or groups of edges in the Object browser.

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Example of a submesh on the edge built using Fixed points 1D hypothesis

See Also a sample TUI Script of a Defining Fixed Points hypothesis operation.


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Copyright © 2003-2007 OPEN CASCADE, EADS/CCR, LIP6, CEA/DEN, CEDRAT, EDF R&D, LEG, PRINCIPIA R&D, BUREAU VERITAS