- specify the diameter of rasterized points
C SPECIFICATION
PARAMETERS
_param1 Specifies the diameter of rasterized points. The
initial value is 1.
DESCRIPTION
glPointSize specifies the rasterized diameter of both
aliased and antialiased points. Using a point size other
than 1 has different effects, depending on whether point
antialiasing is enabled. To enable and disable point
antialiasing, call glEnable and glDisable with argument
GL_POINT_SMOOTH. Point antialiasing is initially disabled.
If point antialiasing is disabled, the actual size is
determined by rounding the supplied size to the nearest
integer. (If the rounding results in the value 0, it is
as if the point size were 1.) If the rounded size is odd,
then the center point (x, y) of the pixel fragment that
represents the point is computed as
( |xw|+.5, |yw|+.5)
where w subscripts indicate window coordinates. All pix-
els that lie within the square grid of the rounded size
centered at (x, y) make up the fragment. If the size is
even, the center point is
( |xw+.5|, |yw+.5|)
and the rasterized fragment's centers are the half-integer
window coordinates within the square of the rounded size
centered at (x, y). All pixel fragments produced in ras-
terizing a nonantialiased point are assigned the same
associated data, that of the vertex corresponding to the
point.
If antialiasing is enabled, then point rasterization pro-
duces a fragment for each pixel square that intersects the
region lying within the circle having diameter equal to
the current point size and centered at the point's (xw,
yw). The coverage value for each fragment is the window
coordinate area of the intersection of the circular region
with the corresponding pixel square. This value is saved
and used in the final rasterization step. The data asso-
ciated with each fragment is the data associated with the
point being rasterized.
Not all sizes are supported when point antialiasing is
enabled. If an unsupported size is requested, the nearest
ified value.
A non-antialiased point size may be clamped to an imple-
mentation-dependent maximum. Although this maximum cannot
be queried, it must be no less than the maximum value for
antialiased points, rounded to the nearest integer value.
GL_POINT_SIZE_RANGE and GL_POINT_SIZE_GRANULARITY are dep-
recated in GL versions 1.2 and greater. Their functional-
ity has been replaced by GL_SMOOTH_POINT_SIZE_RANGE and
GL_SMOOTH_POINT_SIZE_GRANULARITY.
ERRORS
GL_INVALID_VALUE is generated if _param1 is less than or
equal to 0.
GL_INVALID_OPERATION is generated if glPointSize is exe-
cuted between the execution of glBegin and the correspond-
ing execution of glEnd.
ASSOCIATED GETS
glGet with argument GL_POINT_SIZE
glGet with argument GL_ALIASED_POINT_SIZE_RANGE
glGet with argument GL_ALIASED_POINT_SIZE_GRANULARITY
glGet with argument GL_SMOOTH_POINT_SIZE_RANGE
glGet with argument GL_SMOOTH_POINT_SIZE_GRANULARITY
glIsEnabled with argument GL_POINT_SMOOTH
SEE ALSO
glEnable
1