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Table of Contents
glPointSize - specify the diameter of rasterized points
void
glPointSize( GLfloat size )
eqn not supported
- size
- Specifies the diameter of rasterized points.
The initial value is 1.
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
( $ lf ~ x sub w ~ rf ~+~ .5 $, $ lf ~ y sub w
~ rf ~+~ .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
(
$ lf ~ x sub w ~+~ .5 ~ rf$, $ lf ~ y sub w ~+~ .5 ~ rf $)
and the rasterized
fragment's centers are the half-integer window coordinates within the square
of the rounded size centered at ($ 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.
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.
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.
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
glEnable(3G)
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