arcf(3G) arcf(3G)
arcf, arcfi, arcfs - draw a filled circular arc
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.
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.
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 frontfacing
when viewed from the positive z half-space. Some polygon modes
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arcf(3G) arcf(3G)
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 counterclockwise
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.
arc, backface, bgnpolygon, circf, frontface, glcompat, polymode,
polysmooth, scrsubdivide, setpattern, shademodel, subpixel
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 higherquality
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.
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