GEOMETRY SURFACE 3POINTS [snam] [+mid1] pnam1 [+mid2] pnam2 [+mid3] pnam3 [elt]

          

This command is used to create a 3-sided surface from 3 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 three corner points.

elt = element type on the surface. A default element type of TR3 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 three straight lines connecting the corner points, and define a surface based on these three 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 3POINTS S1 P1 P2 P3

Create a three-sided surface S1 with vertices P1, P2, and P3 with the default element type TR3.

2.

GEOMETRY SURFACE 3POINTS S1 P1 P2 P3 TR6

Create a three-sided surface S1 with vertices P1, P2, and P3 with element type TR6.

3.

GEOMETRY SURFACE 3POINTS S1 +P4 P2 P3 +P5 +P6 P1

Create a surface S1 with 3 sides, the first of which is a combined line comprising the lines joining P1 to P4 and P4 to P2; the second side is a line from P2 to P3; and the third side is a combined line comprising the lines joining P3 to P5, P5 to P6 and P6 to P1.

See also the following commands

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