glPointSize — specify the diameter of rasterized points
void glPointSize( | GLfloat | size) ; |
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.
The specified point size is multiplied with a distance attenuation factor and clamped to the specified point size range, and further clamped to the implementation-dependent point size range to produce the derived point size using
where
If multisampling is disabled, the computed point size is used as the point's width.
If multisampling is enabled, the point may be faded by modifying the point alpha value (see glSampleCoverage) instead of allowing the point width to go below a given threshold (see glPointParameter). In this case, the width is further modified in the following manner:
The point alpha value is modified by computing:
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
(
where
and the rasterized fragment's centers are the half-integer window
coordinates within the square of the rounded size centered at
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
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
.
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
.
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_ALIASED_POINT_SIZE_RANGE
glGet with argument GL_POINT_SIZE
glGet with argument GL_POINT_SIZE_MIN
glGet with argument GL_POINT_SIZE_MAX
glGet with argument GL_POINT_FADE_THRESHOLD_SIZE
glGet with argument GL_POINT_DISTANCE_ATTENUATION
glGet with argument GL_SMOOTH_POINT_SIZE_RANGE
glGet with argument GL_SMOOTH_POINT_SIZE_GRANULARITY
glIsEnabled with argument GL_POINT_SMOOTH
Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.