glPointSize(3G) OpenGL Reference glPointSize(3G)
NAME
glPointSize - specify the diameter of rasterized points
C SPECIFICATION
void glPointSize( GLfloat size )
PARAMETERS
size Specifies the diameter of rasterized points. The initial value is
1.
DESCRIPTION
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 GLPOINTSMOOTH.
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
( floor(x )+.5, floor(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
( floor(x +.5), floor(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, or slightly larger than, the current point size
and centered at the point's (x , y ). The total sum of the coverage
w w
values of all produced fragments is the window coordinate area of the
circular point region. The coverage value for each fragment 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
Page 1
glPointSize(3G) OpenGL Reference glPointSize(3G)
implementation. To query the range of supported sizes and the size
difference between supported sizes, call glGet with arguments
GLPOINTSIZERANGE and GLPOINTSIZEGRANULARITY.
NOTES
The point size specified by glPointSize is always returned when
GLPOINTSIZE is queried. Clamping and rounding for aliased and
antialiased points have no effect on the specified value.
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.
ERRORS
GLINVALIDVALUE is generated if size is less than or equal to 0.
GLINVALIDOPERATION is generated if glPointSize is executed between the
execution of glBegin and the corresponding execution of glEnd.
ASSOCIATED GETS
glGet with argument GLPOINTSIZE
glGet with argument GLPOINTSIZERANGE
glGet with argument GLPOINTSIZEGRANULARITY
glIsEnabled with argument GLPOINTSMOOTH
SEE ALSO
glEnable
Page 2