GLPOINTSIZE(3G)GLPOINTSIZE(3G)NAMEglPointSize - specify the diameter of rasterized points
C SPECIFICATION
void glPointSize( GLfloat size )
delim $$
PARAMETERS
size Specifies the diameter of rasterized points. The initial value
is 1.
DESCRIPTIONglPointSize 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
( $ |_ ~ x sub w ~ _| ~+~ .5 $, $ |_ ~ y sub w ~ _| ~+~ .5 $)
where $w$ subscripts indicate window coordinates. All pixels 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
( $ |_ ~ x sub w ~+~ .5 ~ _|$, $ |_ ~ y sub w ~+~ .5 ~ _| $)
and the rasterized fragment's centers are the half-integer window
coordinates within the square of the rounded size centered at ($ x $, $
y $). All pixel fragments produced in rasterizing a nonantialiased
point are assigned the same associated data, that of the vertex
corresponding to the point.
If antialiasing is enabled, then point rasterization produces a
fragment for each pixel square that intersects the region lying within
the circle having diameter equal to the current point size and centered
at the point's ($ x sub w $, $ y sub w $). 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 associated
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 supported size is used.
Only size 1 is guaranteed to be supported; others depend on the
implementation. To query the range of supported sizes and the size
difference between supported sizes within the range, call glGet with
arguments GL_SMOOTH_POINT_SIZE_RANGE and
GL_SMOOTH_POINT_SIZE_GRANULARITY. For aliased points, query the
supported ranges and granularity with glGet with arguments
GL_ALIASED_POINT_SIZE_RANGE and GL_ALIASED_POINT_SIZE_GRANULARITY.
NOTES
The point size specified by glPointSize is always returned when
GL_POINT_SIZE is queried. Clamping and rounding for aliased and
antialiased points have no effect on the specified value.
A non-antialiased point size may be clamped to an
implementation-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 deprecated in GL
versions 1.2 and greater. Their functionality has been replaced by
GL_SMOOTH_POINT_SIZE_RANGE and GL_SMOOTH_POINT_SIZE_GRANULARITY.
ERRORS
GL_INVALID_VALUE is generated if size is less than or equal to 0.
GL_INVALID_OPERATION is generated if glPointSize is executed between
the execution of glBegin and the corresponding 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 ALSOglEnable(3G)
March 1, 2011
