glPointSize(3)

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 argu-
       ment 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 coor-
       dinates  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  frag-
       ment  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  cir-
       cular  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 imple-
       mentation.  To query the range of supported sizes and the size  differ-
       ence  between  supported  sizes within the range, call glGet with argu-
       ments 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-depen-
       dent 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

SEE ALSO

       glEnable(3G)

                                                               GLPOINTSIZE(3G)