CIGAL Reference Manual, Chapter 2 (Commands): CIRCLE
usage: circle [ color vcenter vperim width flag ]
or: circle [ color vcenter radius width flag ]
or: circle [ color cx cy radius width flag ]
or: circle [ color - radius width flag ]
or: circle [ color - - width flag ]
or: circle [ color vperim1 vperim2 vperim3 width flag ]
CIRCLE draws a circle on the graphics display by adding line drawing instructions to the list of graphics vectors. The circle is drawn with intensity COLOR (default COLOR is the value of the internal variable LCOLOR(4)).
The position of the circle is determined by the coordinates of the center and the size of the circle is determined either by specifying a point on the perimeter or by giving the radius. The center coordinates can either be a 3-D vector or explicit X and Y values (in which case Z is set to the current value of the internal variable ZVALUE (see ZVALUE(4))). If the center or radius are not specified then CIRCLE waits for cursor input to specify the missing information.
The WIDTH parameter specifies the width of the lines to be drawn and can take on values 1 to 15.
The FLAG parameter allows you to select various drawing options (these can be combined by addition):
1 - draw shape in absolute coordinates (ignoring transformation and clipping settings). 2 - don't store vectors in VECS (assumed if FLAG & 1). 4 - store lines as individual vectors to facilitate transformations (ignored if FLAG & 3). 8 - paint inside of circle. 16 - XOR values rather than replacing them. 32 - combine (by OR) explicit flag settings with default settings, otherwise the explicit settings replace the default settings 64 - when specifying a circle with the cursor, the 1st point determines the edge & 2nd determines the center (usually 1st is center and 2nd is edge) 128 - define circle by 3 points on perimeter
The default value for FLAG varies depending on the context. If CIRCLE is not called during a SKETCH(2) command then the default FLAG is set at 2. If the coordinate system has been transformed by rotating around either the X or Y axes then FLAG is set at 4 by default (see ROTATE(2), GFLAGS(4)).
BOX(2), ELLIPSE(2), GFLAGS(4), GRAPHICS(1), LCOLOR(4), LINE(2), LWIDTH(4), ROTATE(2), SKETCH(2), ZVALUE(4)