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115 lines
4.8 KiB
Plaintext
115 lines
4.8 KiB
Plaintext
/*!
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\page cartesian_algo_page Body Fitting 3D meshing algorithm
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Body Fitting algorithm generates hexahedrons of a Cartesian grid in
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the internal part of geometry and polyhedrons and other types of
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elements at the intersection of Cartesian cells with the geometrical
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boundary.
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\image html cartesian3D_sphere.png "A sphere meshed by Body Fitting algorithm"
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The meshing algorithm is as follows.
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<ol>
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<li> Lines of a Cartesian structured grid defined by
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\ref cartesian_hyp_anchor "Body Fitting Parameters" hypothesis are
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intersected with the geometry boundary, thus nodes lying on the
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boundary are found. This step also allows finding out for each node of
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the Cartesian grid if it is inside or outside the geometry. </li>
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<li> For each cell of the grid, check how many of its nodes are outside
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of the geometry boundary. Depending on a result of this check
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<ul>
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<li> skip a cell, if all its nodes are outside </li>
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<li> skip a cell, if it is too small according to <b> Size
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Threshold </b> parameter</li>
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<li> add a hexahedron in the mesh, if all nodes are inside </li>
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<li> add a polyhedron or another cell type in the mesh, if some
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nodes are inside and some outside. </li>
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</ul>
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</li>
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</ol>
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To apply this algorithm when you define your mesh, select <b>Body
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Fitting</b> in the list of 3D algorithms and add <b>Body Fitting
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Parameters</b> hypothesis. The following dialog will appear:
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<br>
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\anchor cartesian_hyp_anchor
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<h2>Body Fitting Parameters hypothesis</h2>
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\image html cartesian3D_hyp.png "Body Fitting Parameters hypothesis dialog"
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This dialog allows to define
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<ul>
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<li>\b Name of the algorithm. </li>
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<li> Minimal size of a cell truncated by the geometry boundary. If the
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size of a truncated grid cell is \b Threshold times less than a
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initial cell size, then a mesh element is not created. </li>
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<li> <b> Implement Edges </b> check-box activates incorporation of
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geometrical edges in the mesh.
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\image html cartesian_implement_edge.png "Implement Edges switched off to the left and on to the right"
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<li> <b>Definition mode</b> allows choosing how Cartesian structured
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grid is defined. Location of nodes along each grid axis is defined
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individually:
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<ul>
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<li> You can specify the \b Coordinates of grid nodes. \b Insert button
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inserts a node at \b Step distance (negative or positive) from the
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selected node. \b Delete button removes the selected node. Double
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click on a coordinate in the list enables its edition.
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\b Note that node coordinates are measured along directions of
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axes that can differ from the directions of the Global Coordinate
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System.</li>
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<li> You can define the \b Spacing of a grid as an algebraic formula
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<em>f(t)</em> where \a t is a position along a grid axis
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normalized at [0.0,1.0]. The whole range of geometry can be
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divided into sub-ranges with their own spacing formulas to apply;
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\a t varies between 0.0 and 1.0 within each sub-range. \b Insert button
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divides a selected range into two. \b Delete button adds the
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selected sub-range to the previous one. Double click on a range in
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the list enables edition of its right boundary. Double click on a
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function in the list enables its edition.
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</li> </ul>
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</li>
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<li> <b> Fixed Point</b> group allows defining an exact location of
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a grid node in the direction defined by spacing. The following cases
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are possible:
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<ul>
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<li>If all three directions are defined by spacing, there will
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be a mesh node at the <b> Fixed Point</b>. </li>
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<li>If two directions are defined by spacing, there will be at
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least a link between mesh nodes passing through the <b> Fixed
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Point</b>.</li>
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<li> If only one direction is defined by spacing, there will be
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at least an element facet passing through the <b> Fixed
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Point</b>.</li>
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<li>If no directions are defined by spacing, <b> Fixed Point</b>
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is disabled.</li>
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</ul>
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</li>
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<li> <b> Directions of Axes</b> group allows setting the directions of grid axes.
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<ul>
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<li>If <b> Orthogonal Axes </b> check-box is activated the
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axes remain orthogonal during their modification. </li>
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<li> Selection buttons enable snapping corresponding axes to
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direction of a geometrical edge selected in the Object
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Browser. Edge direction is defined by coordinates of its end
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points.</li>
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<li><b> Optimal Axes</b> button runs an algorithm that tries to
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set the axes to maximize the number of generated hexahedra.</li>
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<li><b> Reset </b> button returns the axes in a default position
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parallel to the axes of the Global Coordinate System.</li>
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</ul>
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</li>
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</ul>
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<br>
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<b>See Also</b> a sample TUI Script of a
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\ref tui_cartesian_algo "Usage of Body Fitting algorithm".
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*/
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