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Body Fitting 3D meshing algorithm

Body Fitting algorithm generates hexahedrons of a Cartesian grid in the internal part of geometry and polyhedrons and other types of elements at the intersection of Cartesian cells with the geometrical boundary.

cartesian3D_sphere.png
A shpere meshed by Body Fitting algorithm

The meshing algorithm is as follows.

  1. Lines of a Cartesian structured grid defined by Body Fitting Parameters hypothesis are intersected with the geometry boundary, thus nodes lying on the boundary are found. This step also allows finding out for each node of the Cartesian grid if it is inside or outside the geometry.
  2. For each cell of the grid, check how many of its nodes are outside of the geometry boundary. Depending on a result of this check
    • skip a cell, if all its nodes are outside
    • skip a cell, if it is too small according to Size Threshold parameter
    • add a hexahedron in the mesh, if all nodes are inside
    • add a polyhedron or another cell type in the mesh, if some nodes are inside and some outside.

To apply this algorithm when you define your mesh, select Body Fitting in the list of 3D algorithms and click "Add Hypothesis" button and "Body Fitting Parameters"" menu item. Dialog of Body Fitting Parameters hypothesis will appear.


Body Fitting Parameters hypothesis

cartesian3D_hyp.png
Body Fitting Parameters hypothesis dialog

This dialog allows to define

  • Name of the algorithm
  • Minimal size of a cell truncated by the geometry boundary. If the size of a truncated grid cell is Threshold times less than a initial cell size, then a mesh element is not created.
  • Cartesian structured grid. Each grid axis is defined individually. Definition mode chooses a way of grid definition:
    • You can specify the Coordinates of grid nodes. Insert button inserts a node at distance Step (negative or positive) from a selected node. Delete button removes a selected node. Double click on a coordinate in the list enables its edition. A grid defined by Coordinates should enclose the geometry, else the algorithm will fail.
    • You can define the Spacing of a grid as an algebraic formula f(t) where t is a position along a grid axis normalized at [0.0,1.0]. The whole range of geometry can be divided into sub-ranges with their own spacing formulas to apply; t varies between 0.0 and 1.0 within each sub-range. Insert button divides a selected range into two ones. Delete button adds the selected sub-range to the previous one. Double click on a range in the list enables edition of its right boundary. Double click on a function in the list enables its edition.


See Also a sample TUI Script of a Usage of Body Fitting algorithm.

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