glPointSize - specify the diameter of rasterized points
void glPointSize(
GLfloat 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 ( x[w] + .5,
y[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[w] + .5, y[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[w]
, y[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(3)
glPointSize(3G)
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