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glPointSize(3G)		       OpenGL Reference		       glPointSize(3G)

NAME    [Toc]    [Back]

     glPointSize - specify the diameter	of rasterized points

C SPECIFICATION    [Toc]    [Back]

     void glPointSize( GLfloat size )

PARAMETERS    [Toc]    [Back]

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

DESCRIPTION    [Toc]    [Back]

     glPointSize specifies the rasterized diameter of aliased, antialiased,
     and multisampled points.  Using a point size other	than 1 has different
     effects depending on whether point	antialiasing is	enabled.  Both point
     antialiasing and multisampling may	affect the actual point	size.  To
     enable and	disable	point antialiasing, call glEnable and glDisable	with
     argument GL_POINT_SMOOTH.

     If	point antialiasing and multisampling are both 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  | + .5, | y	| + .5)
				 w	      w

     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  + .5	|, | y	+ .5 |)
				 w	      w

     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 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	, y ).	The coverage value for each fragment is	the window
	       w   w
     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

									Page 1

glPointSize(3G)		       OpenGL Reference		       glPointSize(3G)

     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

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 implementationdependent
 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.

     versions 1.2 and greater.	Their functionality has	been replaced by

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_SMOOTH_POINT_SIZE_RANGE
     glIsEnabled with argument GL_POINT_SMOOTH

SEE ALSO    [Toc]    [Back]


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