arc(3G) arc(3G)
NAME
arc, arci, arcs - draw a circular arc
C SPECIFICATION
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
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
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
arcf, bgnclosedline, circ, crvn, linewidth, linesmooth, lsrepeat,
scrsubdivide, setlinestyle, shademodel, subpixel
BUGS
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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