GEOMETRY SURFACE 4POINTS [snam] [+mid1] pnam1 [+mid2] pnam2 [+mid3] pnam3 [+mid4] pnam4 [elt]

          

This command is used to create a 4-sided surface from 4 points. An extended form of the command allows the automatic creation of combined lines for the sides of the surface by allowing mid-side points to be specified.

snam = name of the surface, used for later references to the surface.

+mid = names of mid-side points used to define new combined lines. There may be more than one mid-side point on a side of the surface.

pnam = names of the four corner points.

elt = element type on the surface. A default element type of QU4 will be assumed if `elt' is omitted. Refer to command MESHING TYPES for a detailed description.

In the case where no mid-side points are present, FEMGEN will generate four straight lines connecting the corner points, and define a surface based on these four lines. Where lines already exist between any of the points, new lines will not be created, rather the existing lines will be used in the definition.

In the extended form of the command, either cursor picking or keyboard input can be used to distinguish between corner points and mid-side points. With the cursor, the left button is used to specify a corner point and the middle button (or right button on a two button mouse) is used to specify a mid-side point. With the keyboard, a corner point is typed normally while a mid-side point is immediately preceded by a `+' (plus sign).

The order in which points are specified is different if mid-side points are present. This enables simple termination of the command. Each side is identified by its end point (whereas in the case of a surface without mid-side points it is identified by its start point). Thus the definition of the surface is completed by specifying the end point of the last side (this is also the start point of the first side).

Return Level: GEOMETRY SURFACE

Examples:

1.

GEOMETRY SURFACE 4POINTS S1 P1 P2 P3 P4

Create a four-sided surface S1 with vertices P1, P2, P3, and P4 with the default element type QU4.

2.

GEOMETRY SURFACE 4POINTS S1 P1 P2 P3 P4 QU8

Create a four-sided surface S1 with vertices P1, P2, P3, and P4 with element type QU8.

3.

GEOMETRY SURFACE 4POINTS S1 +P2 +P3 P4 P5 P6 +P7 P1

Create a surface S1 with 4 sides, the first of which is a combined line comprising the lines joining P1 to P2, P2 to P3 and P3 to P4; the second side is a line from P4 to P5; the third side is a line from P5 to P6; and the fourth side is a combined line comprising the lines joining P6 to P7 and P7 to P1.

See also the following commands

'LABEL GEOMETRY SURFACES'
'UTILITY DELETE SURFACES'
'UTILITY TABULATE GEOMETRY SURFACES'
'VIEW GEOMETRY'