arcf(3G)

NAME
     arcf, arcfi, arcfs - draw a filled circular arc

C SPECIFICATION
     void arcf(x, y, radius, startang, endang)
     Coord x, y, radius;
     Angle startang, endang;

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

     void arcfs(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 filled arc. The
                center of the filled arc is the center of the circle that
                would contain the arc.

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

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

     startang   expects the measure (in tenths of a degree) of the start angle
                of the filled arc.  The start angle of the filled arc is
                measured relative to the positive x-axis.

     endang     expects the measure (in tenths of a degree) of the end angle
                of the filled arc.  The end angle of the filled arc is
                measured relative to the positive x-axis.

DESCRIPTION
     arcf draws a filled circular arc in the x-y plane (z = 0).  The filled
     area is bound by the arc and by the start and end radii. 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 single polygon, and therefore inherits all
     properties that affect the drawing of polygons.  These include the
     current color, writemask, fill pattern, shade model, polygon antialiasing
     mode, polygon scan conversion mode, and subpixel mode.  Front-face and
     back-face elimination work correctly with filled arcs, which are front-
     facing when viewed from the positive z half-space.  Some polygon modes
     are applicable only if old-style scan conversion is defeated.  (See note
     below.)

     A filled arc is defined in terms of the circle that contains it.  All
     references to the radius and the center of the filled arc refer to the
     radius and center of the circle that contains the filled arc. The angle
     swept out by the filled 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, a filled 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 filled circle.

     After arcf executes, the graphics position is undefined.

SEE ALSO
     arc, backface, bgnpolygon, circf, frontface, glcompat, polymode,
     polysmooth, scrsubdivide, setpattern, shademodel, subpixel

NOTE
     By default arcf draws a polygon using the old-style scan conversion
     algorithm, rather than the point sampling algorithm used by bgnpolygon
     and endpolygon.  Point sampling is prefered over old-style scan
     conversion because it has higher performance, it results in higher-
     quality images when blending, logical operations, or stenciling are used,
     and it supports new rendering features such as texture mapping, fog, and
     antialiasing.  Call glcompat(GLC_OLDPOLYGON,0) to enable point sampling
     of polygons generated by arcf.