fglPointSize(3G) OpenGL Reference fglPointSize(3G)NAME
fglPointSize - specify the diameter of rasterized points
FORTRAN SPECIFICATION
SUBROUTINE fglPointSize( REAL*4 size )
PARAMETERS
size Specifies the diameter of rasterized points. The initial value is
1.
DESCRIPTION
fglPointSize 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 fglEnable and fglDisable 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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fglPointSize(3G) OpenGL Reference fglPointSize(3G)
implementation. To query the range of supported sizes and the size
difference between supported sizes within the range, call fglGet with
arguments GL_SMOOTH_POINT_SIZE_RANGE and
GL_SMOOTH_POINT_SIZE_GRANULARITY. For aliased points, query the
supported ranges and granularity with fglGet with arguments
GL_ALIASED_POINT_SIZE_RANGE and GL_ALIASED_POINT_SIZE_GRANULARITY.
NOTES
The point size specified by fglPointSize 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 fglPointSize is executed between the
execution of fglBegin and the corresponding execution of fglEnd.
ASSOCIATED GETS
fglGet with argument GL_POINT_SIZE
fglGet with argument GL_ALIASED_POINT_SIZE_RANGE
fglGet with argument GL_ALIASED_POINT_SIZE_GRANULARITY
fglGet with argument GL_SMOOTH_POINT_SIZE_RANGE
fglGet with argument GL_SMOOTH_POINT_SIZE_GRANULARITY
fglIsEnabled with argument GL_POINT_SMOOTH
SEE ALSO
fglEnable
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