`zone generate`

command

Syntax

- zone generate keyword
Primary keywords:

from-building-blocks from-sketch from-topography from-geometry

Generate zones based on an algorithm—generally from some other data structure. The following keywords are available:

- from-building-blocks <set s > (3D Only)
Generate zones from the current i Building Blocks set. See the c building blocks commands. If the optional keyword

`set`

is used, zones are generated from the set named s instead of the current set.

- from-sketch <keyword ...>
Generate zones from the current i Sketch set.

- area-check b
Specify if areas of underlying sub-elements should be checked when generating zones. Default values is

`true`

. An error will be generated if`area-check`

is set to`true`

and the area of a triangular sub-element in each overlay \(\le\) 10% of the whole element area (in 2D Sketch Pane).

- from-topography <keyword ...> <range> (3D Only)
Generate zones by extruding surface faces in the range until they meet polygons in a geometric set.

Discussion and examples on the use of this option to create zones can be found in Surface Topography and Layering.

- geometry-set s
Specify the geometry set used to define the surface to which zones are being extruded. By default the current geometric set will be used.

- segments i
Specify the number of zone layers created between the existing surface zone faces and the geometry set. By default this value is 1.

- direction v
Specify the extrusion direction that will be used to create zones on surface faces. From a surface gridpoint, a ray will be cast in this direction until it intersects a polygon in the geometric set. This will define the shape and size of the zones created. By default this value will be (0,0,1). If a face normal is parallel to this direction vector (with a tolerance of about 0.5 degrees) the face will be neglected even it if is in the range.

- ratio f
Specify the ratio used to distribute zones from the surface face to the geometric set. A ratio of 1.1 means that each zone edge in that direction will be 1.1 times the length of the previous zone. If not specified, the default ratio is 1.0.

- from-geometry <keyword ...> (3D Only)
Generate zones by identifying closed volumes in a geometric set, and creating zones that fill the volume. The command operates in three steps: first, original surfaces (faces) are triangulated to create an initial coarse mesh; second, the initial mesh is remeshed with triangular or mixed (quad-dominant mode) elements using user specified parameters; third, the volume mesher is called to fill the volumes with tetrahedral or mixed (hex-dominant mode) zones. By default, hex-dominant mode is used (quad-dominant for surface meshes). Note that input surfaces should be planar for proper triangulation.

The following optional keywords are available.

- set s
Specify the geometry set used to define the surface to which zones are being extruded. By default the current geometric set will be used.

- minimum-edge f
Specify the minimum surface element size f > 0 along the edges. The actual size will be close to this value, but the result is not guaranteed to be exact.

- maximum-edge f
Specify the maximum surface element size f > 0 along the edges. The actual size will be close to this value, but the result is not guaranteed to be exact.

- size-surface f
Specify desired element size on surface meshes. The element size tends (according to the

`gradation-surface`

parameter) toward this value (if > 0) as they get away from the edges. This parameter can be used to make surface elements finer or coarser. The default value of 0 means that the size will be determined automatically based on the element sizes along the edges.

- gradation-surface f
Specify gradation f > 0 of the element sizes along the edges (gradation from

`minimum-edge`

to`maximum-edge`

) and inside the surface meshes (when`size-surface`

is specified). A value close to 0 leads to a more progressive variation. The default value is 0.5.

- size-volume f
Specify desired zone size inside the closed volumes. The zone size tends toward this value as they get away from the bounding surfaces (surface meshes). The default value of 0 means that the size will be determined automatically based on the size of surface elements.

- gradation-volume f
Specify gradation f > 0 of the zone sizes from the surface elements sizes to the size defined by the

`size-volume`

parameter inside the closed volumes. A value close to 0 leads to a more progressive variation. The default value is 0.5.

- cut-angle f
Specify cut angle for delimiting initial surfaces patches (groups of connected triangles in the initial triangulated mesh) used for surface remeshing. An angle between two adjacent triangles greater than this value will draw a limit between two patches. A small value tends to give numerous small patches and the final mesh will be close to the initial mesh but may be of poor quality. A bigger value tends to give fewer bigger patches which are better for remeshing but the final mesh may be more distant from the initial mesh (increased geometric error). The default value is 20° and a value of 45° should be considered as the maximum.

- tetrahedron
If specified, only tetrahedral zones will be generated.

- bring-to-building-blocks
If specified, then the result of the volume discretization will also be sent to a building-blocks set.

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