- specify the diameter of rasterized points



C SPECIFICATION


PARAMETERS

       _param1  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

                          ( |xw|+.5, |yw|+.5)

       where  w subscripts indicate window coordinates.  All pix-
       els 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

                          ( |xw+.5|, |yw+.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  ras-
       terizing  a  nonantialiased  point  are  assigned the same
       associated data, that of the vertex corresponding  to  the
       point.

       If  antialiasing is enabled, then point rasterization pro-
       duces 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  asso-
       ciated  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
       ified value.

       A  non-antialiased  point size may be clamped to an imple-
       mentation-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 dep-
       recated in GL versions 1.2 and greater.  Their functional-
       ity  has  been  replaced by GL_SMOOTH_POINT_SIZE_RANGE and
       GL_SMOOTH_POINT_SIZE_GRANULARITY.


ERRORS

       GL_INVALID_VALUE is generated if _param1 is less  than  or
       equal to 0.

       GL_INVALID_OPERATION  is  generated if glPointSize is exe-
       cuted between the execution of glBegin and the correspond-
       ing 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



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