2003-2004
Silicon Graphics, Inc.
glPointSize
3G
glPointSize
glPointSize
glPointSizex
specify the diameter of rasterized points
C Specification
void glPointSize
GLfloat size
void glPointSizex
GLfixed size
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
xy
of the pixel fragment that represents the point is computed
as
[
xw
]
+
12
[
yw
]
+
12
where w
subscripts indicate window coordinates. All pixels that lie
within the square grid of the rounded size centered at
xy
make up the fragment. If the size is even, the center point
is
[
xw
+
12
]
[
yw
+
12
]
and the rasterized fragment's centers are the
half-integer window coordinates within the square of the
rounded size centered at
xy
.
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
xw
yw
.
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, call
glGet
with the argument
GL_SMOOTH_POINT_SIZE_RANGE.
For aliased points, query the supported ranges
glGet
with the argument
GL_ALIASED_POINT_SIZE_RANGE.
Notes
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.
Errors
GL_INVALID_VALUE is generated if
size is less than or equal to 0.
Associated Gets
glGet
with argument GL_ALIASED_POINT_SIZE_RANGE
glGet
with argument GL_SMOOTH_POINT_SIZE_RANGE
See Also
glEnable,
glGet
Copyright
Copyright 2003-2004
Silicon Graphics, Inc. This document is licensed under the SGI
Free Software B License. For details, see
https://khronos.org/registry/OpenGL-Refpages/LICENSES/LicenseRef-FreeB.txt.