Meshing

Default Meshing Parameters

Any closed (watertight) polygon can be meshed in the Extruder. Structured mesh can be used only for simply-connected 3- or 4-sided polygons, while unstructured mesh can be applied to any closed polygon. The following options control mesh construction.

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Basic Parameters

Create unstructured meshes only

If this option is checked, unstructured mesh is used for all blocks including regular 3- and 4-sided polygons which are otherwise meshed with structured mesh.

When only unstructured mesh is used and mesh mode (next parameter) is checked, 3-sided polygons will be meshed with quadrilaterals only (if amount of zones per perimeter is even).

Use only quads in unstructured meshes

If this option is checked, the mesher will attempt to build meshes containing only quadrilaterals. However, under certain conditions, the mesher may fail to create quadrilateral mesh (e.g. odd number of zones per block perimeter); an error will be displayed in this case.

Target zone size

This parameter specifies desired zone size (target size) inside of a block, f ≥ 0. The default value is 0.

The target-size is the radius of a circle encompassing a quadrilateral or triangular zone. Zone sizes tend toward this value as they get away from the block boundaries. The target zone size may be smaller or bigger than the default zone sizes specified at the block edges.

Max gradation

This parameter specifies maximum gradation f > 0 for the unstructured mesher. The default value is 0.5.

The parameter controls the gradation of zone sizes from those specified on block boundaries to the size defined by target zone size inside of the block. A value close to 0 leads to a more progressive variation of zone sizes (smoother).

Advanced Parameters

Optimization level

This parameter specifies optimization level 0 ≤ i ≤ 10 for the unstructured mesher. The default value is 5.

A zero value makes the mesher to skip the optimization step. The speed is maximal but the quality may be poor. From value 1 on, the optimization algorithm uses several techniques to improve both the shape quality and the size quality of the zones. Level 5 is usually a good trade-off between quality and speed.

Shape quality weight

This parameter specifies value for the shape quality 0 ≤ f ≤ 1 for the unstructured mesher. The default value is 0.7.

The parameter controls the trade-off between shape optimization and size optimization. It is the weight of the shape quality in the measure of the global quality of a zone. The default value (0.7) gives a slight preference to the shape quality over the size quality.

Weight on quadrilaterals

This parameter specifies weight on quadrilaterals 0 ≤ f ≤ 1 for the unstructured mesher. The default value is 0.75. This parameter is not used for quad-only unstructured meshes.

The parameter controls the trade-off between a higher ratio of quads and a better mesh with more triangles:

  • with f = 0, quadrilaterals are never used,
  • with f = 0.5, quadrilaterals are used only when they improve the quality of the mesh (when a quadrilateral is better than two triangles),
  • for 0.5 < f < 1, quadrilaterals are more and more used even if this leads to a lesser global quality of the mesh,
  • with f = 1, the minimum number of triangles is used to get a valid mesh (it may be of poor quality).

The default value (0.75) gives a significant preference to the quad / triangle ratio over the mesh quality.

Automatic Meshing

Zoning refers to the process of assignment of specific number of zones per edge (or specifying edge size) in the construction view and/or changing the size of an extrusion stage in the the extrusion view. Changing edge size affects meshing, therefore if a set already contains any blocks with unstructured mesh, it will be deleted. Blocks with structured mesh can be dynamically remeshed.

Automatic zoning is accessed by clicking the Autozone tool (autozonecmd) on the toolbar which shows a dialog as seen here.

Choose one of three autozoning modes described below.

Zone Length

  • Specifies the desired zone edge size in model units. Zone size will increase as this number increases. This zoning type is applied to the current view only. Applying this zoning will overwrite any zoning already specified in the current view of the extrusion set.

Model Extent

  • Specifies the number of zones to apply across the extent of the model (this is the larger of the two dimensions when used in the construction view). Zone size will decrease as this number increases. This zoning is applied to the current view only. Applying this zoning will overwrite any zoning already specified in the current view of the extrusion set.

Total Number of Zones

  • Specifies the total number of zones in the model accounting for initially meshed blocks in the construction view and geometry set in the extrusion view (thus, extrusion depth has to be non-zero). This option is only available and applies to blocks with structured mesh. To enable the option:

    • Make sure that meshing parameters are not set to use unstructured mesh only,
    • Split or remove all irregular blocks and polygons,
    • Block all polygons with the default number of zones,
    • Specify extrusion depth.

    Zone size will decrease as total number of zones increases. This zoning is applied to both the extrusion view and the construction view at the same time, regardless of which is the active (visible) view. Applying this zoning will overwrite any existing zoning already specified in the extrusion set.