arc(3G)								       arc(3G)

NAME    [Toc]    [Back]

     arc, arci,	arcs - draw a circular arc

C SPECIFICATION    [Toc]    [Back]

     void arc(x, y, radius, startang, endang)
     Coord x, y, radius;
     Angle startang, endang;

     void arci(x, y, radius, startang, endang)
     Icoord x, y, radius;
     Angle startang, endang;

     void arcs(x, y, radius, startang, endang)
     Scoord x, y, radius;
     Angle startang, endang;

     All of the	routines named above are functionally the same.	 They differ
     only in the type assignments of their parameters.

PARAMETERS    [Toc]    [Back]

     x		expects	the x coordinate of the	center of the arc. The center
		of the arc is the center of the	circle that would contain the
		arc.

     y		expects	the y coordinate of the	center of the arc.  The	center
		of the arc is the center of the	circle that would contain the
		arc.

     radius	expects	the length of the radius of the	arc.  The radius of
		the arc	is the radius of the circle that would contain the
		arc.

     startang	expects	the measure of the start angle of the arc. The start
		angle of the arc is measured from the positive x-axis.

     endang	expects	the measure of the end angle of	the arc. The end angle
		of the arc is measured from the	positive x-axis.

DESCRIPTION    [Toc]    [Back]

     arc draws an unfilled circular arc	in the x-y plane (z = 0). To draw an
     arc in a plane other than the x-y plane, define the arc in	the x-y	plane
     and then rotate or	translate the arc.

     An	arc is drawn as	a sequence of line segments, and therefore inherits
     all properties that affect	the drawing of lines.  These include the
     current color, writemask, line width, stipple pattern, shade model, line
     antialiasing mode,	and subpixel mode.  The	stipple	pattern	is initialized
     to	bit zero of the	current	linestyle before the arc is drawn, then
     shifted continuously through the segments of the arc.






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arc(3G)								       arc(3G)



     An	arc is defined in terms	of the circle that contains it.	 All
     references	to the radius and center of the	arc refer to the radius	and
     center of the circle that contains	the arc. The angle swept out by	the
     arc is the	angle from the start angle counter-clockwise to	the end	angle.

     The start and end angles are defined relative to the positive x-axis. (To
     speak more	precisely, because the arc might not be	centered on the
     origin, the start and end angles are defined relative to the right
     horizontal	radius of the circle containing	the arc).  Positive values for
     an	angle indicate a counter-clockwise rotation from the horizontal.
     Negative values indicate a	clockwise rotation from	the horizontal.

     The basic unit of angle measure is	a tenth	of a degree. The value 900
     indicates an angle	of 90 degrees in a counter-clockwise direction from
     the horizontal. Thus, an arc that spans from a start angle	of 10 degrees
     (startang = 100) to an end	angle of 5 degrees (endang = 50) is almost a
     complete circle.

     After arc executes, the graphics position is undefined.

SEE ALSO    [Toc]    [Back]

     arcf, bgnclosedline, circ,	crvn, linewidth, linesmooth, lsrepeat,
     scrsubdivide, setlinestyle, shademodel, subpixel

BUGS    [Toc]    [Back]

     When the line width is greater than 1, small notches will appear in arcs,
     because of	the way	wide lines are implemented.


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