CONSTRUCT LINE Contents [line_name] Mode [Range]

                      

FEMVIEW Command only.

This command enables the user to define a line through the mesh. This line may be a line of NODES, a line of ELEMENTS (see note 5) or a FREE line depending on the selection made for its contents. If the line is to contain nodes or elements then it may be defined in one of the following ways.

Mode Range Comments

THROUGH n1 n2 [n3....] [ANGLE Toll] See notes 1 and 4. /PICK [ANGLE Toll]

LIST n1 n2 n3 .... The line is defined as connecting the

n1 TO n2 nodes or elements in the specified order.

n1 TO n2 STEPS n3 (See notes 2 and 4). /PICK

IJK [BLOCK n] I n1 TO n2 The line of nodes or elements specified by node

... J n3 TO n4 K n5 TO n6 or element IJK values is defined. This command is for IJK regular models only. Note that if no BLOCK is specified the default is the 1st block and that any IJK range not specified defaults to n1 - nmax. Note also that only one direction can have a TO range (or default range) specified. (ie: only one axis can have `n2' different to `n1').

If a FREE line is being constructed then this line is defined by either two cursor hits or two node numbers (see note 3).

If a line name is specified in the command then the line will be saved in the database under this name. This line can then be recovered later, for example to display results or plot a graph along it.

 

Figure 2.4: Definition of Toll

Notes:

1.

Line `THROUGH' reference nodes
The CONSTRUCT LINE NODES THROUGH n1 n2 command identifies nodes on a straight line between nodes `n1' and `n2'. A line of elements cannot currently be defined in this way. If `THROUGH n1 n2 ...nn' is specified then nodes on line segments between `n1' to `n2', `n2' to 'n3',..., `nn-1' to `nn', are identified. Nodes within a solid of revolution formed by sweeping a circular arc about each line segment are identified. The circular arc is defined with the line segment as a cord and the angle `Toll' being the sum of the angles subtended from the cord to a point on the arc. A default angle of 1 degree is used in normal operation. If `ANGLE Toll' is entered, then the angle specified will replace the 1 degree default in the algorithm.

2.

Simple `LIST' of nodes or elements
The line is defined as connecting the nodes or elements in the order they are specified. It is possible to continue entry of a simple list of nodes/elements on the subsequent input line by using the special continuation character `:' at the end of a line. The program will then prompt for more input with `MORE$\gt$'.

CONSTRUCT LINE NODES LIST 1 4 7 12 16 25 91 118 121 139 55 56 :
MORE> 35 51 235 236 100 103 106 109 111 45 146 158

3.

An arbitrary or `FREE' line
The `FREE' line is one that does not necessarily pass through node points. It can only be used on 2D planar models or on cross-sections taken through 3D models. The line is defined either by making two cursor hits or by giving the numbers of two node points.

4.

Use of the graphics cursor to `/PICK' nodes
The command word `/PICK' enables the user to select nodes or elements for the definition of a line by using the graphics cursor. For a node or element to be sensitive to the cursor it must be visible in the current `VIEW' mode. To terminate cursor picking it is necessary to make two approximately coincident cursor hits, or to move the cursor outside the graphics area.

5.

Element lines
Element lines are taken to be lines connecting the centroids of the specified elements. Currently element lines may only be used when plotting graphs.

6.

Maximum number of nodes/elements
The maximum number of nodes or elements in a line is 1000. There is no limit to the length of a FREE line.

Examples:

1.

CONSTRUCT LINE NODES THROUGH 9 108

A line of nodes is defined with all the nodes that lie on a straight line between nodes 9 and 108.

2.

CONSTRUCT LINE NODES THROUGH 4 10 30 40 50 65 ANGLE 5.0

A line of nodes is defined with all the nodes that lie on or within 5 degrees of the line segments 4 to 10, 10 to 30, 30 to 40, 40 to 50 and 50 to 65.

3.

CONSTRUCT LINE NODES boundary THROUGH /PICK

The cursor is made available to pick the nodes that define the line segments that the nodes must be on. The line is then saved in the database under the name `boundary'.

4.

CONSTRUCT LINE NODES LIST 1 TO 20 STEP 3

A line of nodes 1, 4, 7, 10, 13, 16 and 19 is defined.

5.

CONSTRUCT LINE NODES top_edge LIST 1 TO 50

A line of nodes from 1 to 50 is defined and saved in the database under the name `top_edge'.

6.

CONSTRUCT LINE ELEMENTS LIST 1 4 7 12 16 19 112 115 118 201

A line of the elements listed is defined.

7.

CONSTRUCT LINE NODES LIST /PICK

The cursor is made available to pick the nodes which are on the line.

8.

CONSTRUCT LINE FREE /CURSOR

The cursor is made available to identify any two positions that define a line that will cut a 2D planar model.

9.

CONSTRUCT LINE FREE diagonal 3 112

A line passing freely through a 2D planar model from node 3 to node 112 is defined and saved in the database under the name `diagonal'.

10.

CONSTRUCT LINE NODES IJK I 51 J 1 TO 6 K 7

For an IJK regular model only, a line is defined from nodes J1 to J6 on the plane I51, K7.

11.

CONSTRUCT LINE ELEMENTS IJK BLOCK 3 I 51 J 1

For an IJK regular model only, a line is defined in block 3 from elements K1 to Kmax on the plane I51, J1.

See also the following commands

'PRESENT GRAPH LINE'
'UTILITY DELETE LINES'
'UTILITY TABULATE LINES'
'VIEW LINE'