It might be helpful to extract parts of a 2d or 3d grid.
Algebraic grids could e.g. read in, the border extracted the polygons splined and transformed into point distributions. Then first layers can be build on these distributions and finally elliptic smoothing can be applied to the original grid.
It is also possible to throw away a block of a complex grid and fill the empty space with a new block after extracting the boundary faces of the neighbouring blocks.

General Syntax

extract_entities EntityIndex Type Face Min1 Max1 Stp1 Min2 Max2 Stp2 Min3 Max3 Stp3

where Type describes the type of extraction, i.e.
1 = 3D from 3D
2 = 2D from 3D
3 = 2D from 2D
4 = 1D from 3D
5 = 1D from 2D

and nFace the wished constant plane which could be
1 = I-Face
2 = J-Face
3 = K-Face
The min. and max. values, as well as the step size are explained in the specific examples.

Extracting 3D grids from 3D grids

 Extract a 3D sub-block from an existing 3D grid. Of course, the nFace variable does not make sens here and can be set to any value. Dimensions and step sizes for the i,j,k directions can be choosen within the limits of the existing block.

Usage:

Result: Parameters: Example:

- Given: block with the dimensions lImax, lJmax, lKmax
- Wanted: block with the half extension in k-direction

extract_entities BlockIndex 1 0 0 lImax-1 1 0 lJmax-1 1 0 (lKmax-1)/2 1

Extracting 2D surfaces from 3D grids

2d grid planes can be extracted of either i=const., j=const., or k=const., but not mixed. The actual plane and its dimensions will be choosen using the grid browser

Usage:

Result: Parameters:

IMPORTANT: To know which are the dim1 and dim2 extensions of the selected face type consider the following:
Face Type 1: dim1 = j-, dim2 = k-direction of the block
Face Type 2: dim1 = i-, dim2 = k-direction of the block
Face Type 3: dim1 = i-, dim2 = j-direction of the block

Example:

- Given: block with the dimensions lImax, lJmax, lKmax
- Wanted: face which is the Jmin-Face of the block

extract_entities BlockIndex 2 2 0 0 1 0 lImax-1 1 0 lKmax-1 1

Extracting 2D surfaces from 2D surface grids

2d sub grids can be extracted from 2d grids. Of course, the value of the Face Type is unimportant.

Usage:

Result: Parameters:

IMPORTANT: The extension of the resulting grid vary between 1 and lImax for i-direction as well as between 1 and lJmax for j-direction.

Example:

- Given: face with the dimensions lImax, lJmax
- Wanted: face with the same i-extension, from N to M in j-direction

extract_entities BlockIndex 3 0 1 lImax 1 N M 1 0 0 0

Extracting 1D line from 3D grids

1d lines can be extracted from 3d grids. Through the selected face type The actual line will be choosen using the grid browser

Usage:

Result: Parameters:

IMPORTANT: At this time, either the number of elements in dim1 or in dim2 must be equal 1. The way to determine dim1 and dim2 is explained in 2D from 3D extraction.

Example:

- Given: block with the dimensions lImax, lJmax and lKmax
- Wanted: two edges on j-faces using the complete dimension in i-direction

extract_entities BlockIndex 4 2 0 lJmax-1 lJmax-1 0 lImax-1 1 0 0 0

Extracting 1D lines from 2D surface grids

Usage:

Result: Parameters:

{Build by Martin Hepperle} {Rebuild 845: Saturday, 31, 1997 at 11:46:32, March, by Olaf Brodersen}