Интерактивная система просмотра системных руководств (man-ов)
glPointSize (3)
>> glPointSize (3) ( Разные man: Библиотечные вызовы )
NAME
glPointSize
- specify the diameter of rasterized points
C SPECIFICATION
void glPointSize(
GLfloat size )
delim $$
PARAMETERS
size
Specifies the diameter of rasterized points.
The initial value is 1.
DESCRIPTION
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 sub w ~ _| ~+~ .5 $, $ |_ ~ y sub 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 sub w ~+~ .5 ~ _|$, $ |_ ~ y sub 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 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.
NOTES
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.
ERRORS
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.
ASSOCIATED GETS
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
