Command: ellipse

Syntax

{<entity> = } ellipse

Description

Create an ellipse or elliptical arc graphic entity, or a series of points forming a full ellipse or elliptical arc.

Parameters

• <entity>
  An entity or gstructure identifier. The ellipse entity will be given this name.

Switches

• -alph=<num>
  An alpha transparency factor between 0 and 1. A value 1 implies fully opaque, 0 means fully transparent (therefore invisible). The default is 1.

• -ap=<num>
  Number of line approximations used when drawing or calculating the ellipse. If omitted, the default curve approximation value def_approx is used.

• -a1=<num>
  The start angle when an elliptical arc is required. This is measured from point p1.

• -a2=<num>
  The end angle when an elliptical arc is required. This is measured from point p1. If neither -a1 nor -a2 is present, a full ellipse results.

• -br=<num>
  A brightness factor between -1 and +1. A value 0 means normal, -1 means very dark (black), +1 means very bright (white). The default is 1.

• -c=<point>
  The ellipse center of curvature. The default is the current value of graphic control, or is computed from other parameter values.

• -col=<color>
  The color of the ellipse. If included, this will override any color defined in the linestyle (-ls). If omitted, the value no_change is used.

• -fr=<num>
  Define a fragment number for the entity. If omitted, the default fragment def_fragment is used.

• -g=<groups>
  The graphic groups of which the entity is to be a part.

• -ls=<linestyle | color>
  The linestyle of the ellipse. This may be a linestyle or color. If omitted, the current modeling color (def_color) is used.

• -n=<direction>
  The normal to the plane of the ellipse. The default is up, or is computed from other parameter values.

• -o=A|C
  The orientation of the ellipse: C for clockwise or A for counterclockwise (anticlockwise). Counterclockwise is the default.

• -op=<ident>
  A point identifier into which points along the ellipse are to be recorded. This option is not available when an entity is being created. If <ident> does not exist a new point array is created using current scope rules.

• -p1=<point>
  The point at the end of the major axis on the ellipse, or the direction toward it relative to the center of curvature.

• -p2=<point>
  The point at the end of the minor axis on the ellipse, or the direction toward it relative to the center of curvature.

• -ra=<num>
  Define a rank for the entity. If omitted, the default rank def_rank is used.

• -r1=<num>
  The major radius. If omitted, it is computed from other parameter values.

• -r2=<num>
  The minor radius. If omitted, it is computed from other parameter values.

• -th=<num>
  The thickness of the ellipse. If included, this will override any thickness defined in the linestyle (-ls).

Notes

If the command has the form <entity> = ellipse, an entity is always created.

If the command has no entity assignment, then an entity will be created only if the -op option is not used, or the command is not within another entity creation block, e.g. lines, polygon.

All point parameter expressions are computed relative to the last computed point parameter.

Examples

Create an unnamed ellipse entity.

ellipse -c=p0, -r1=1000, -r2=300

Create a named ellipse entity (90 degree sweep).

entity my_ell = ellipse -p1=e:100, -p2=n:200, -a1=0,\ 
    -a2=90, -col=red

Store ellipse points into an array (no entity created).

point eps[]
ellipse -c=(10,10,0), -p1=e:5000, -p2=n:4000, -op=eps

Add ellipse points during the creation of a polygon entity.

polygon -no_draw {
    gc, e:1000, n:200
    ellipse -c=n:300, -p1=n:300, -p2=e:50, -a1=0,\ 
       -a2=180, -ap=32
    n:200, w:1000, r
}

See Also