glPointSize

GLPOINTSIZE(3G)						      GLPOINTSIZE(3G)



NAME
       glPointSize - specify the diameter of rasterized points


C SPECIFICATION
       void glPointSize( GLfloat 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	 dis-
       abled.

       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	frag-
       ment that represents the point is computed as

				( ⌊xw⌋+.5, ⌊yw⌋+.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

				( ⌊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 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 (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 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-
       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.

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)