glPointSize(3G) OpenGL Reference glPointSize(3G)
glPointSize - specify the diameter of rasterized points
void glPointSize( GLfloat size )
size Specifies the diameter of rasterized points. The initial value is
1.
glPointSize specifies the rasterized diameter of aliased, antialiased,
and multisampled points. Using a point size other than 1 has different
effects depending on whether point antialiasing is enabled. Both point
antialiasing and multisampling may affect the actual point size. To
enable and disable point antialiasing, call glEnable and glDisable with
argument GL_POINT_SMOOTH.
If point antialiasing and multisampling are both 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 | + .5, | y | + .5)
w w
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 + .5 |, | y + .5 |)
w w
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 , y ). The coverage value for each fragment is the window
w w
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
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glPointSize(3G) OpenGL Reference glPointSize(3G)
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 implementationdependent
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
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