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  man pages->Tru64 Unix man pages -> glPointSize (3)              



NAME    [Toc]    [Back]

       glPointSize - specify the diameter of rasterized points

SYNOPSIS    [Toc]    [Back]

       void glPointSize(
               GLfloat size );

PARAMETERS    [Toc]    [Back]

       Specifies  the  diameter of rasterized points. The initial
       value is 1.

DESCRIPTION    [Toc]    [Back]

       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[w] + .5,
       y[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[w] + .5,  y[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

       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[w]
       ,  y[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

NOTES    [Toc]    [Back]

       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.

 in GL versions 1.2 and greater.  Their functionality
 has been replaced  by  GL_SMOOTH_POINT_SIZE_RANGE  and

ERRORS    [Toc]    [Back]

       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    [Toc]    [Back]

       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    [Toc]    [Back]


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