fglPointSize(3G)

NAME
     fglPointSize - specify the diameter of rasterized points


FORTRAN SPECIFICATION
     SUBROUTINE fglPointSize( REAL*4 size )


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

DESCRIPTION
     fglPointSize 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 fglEnable and fglDisable 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

                           ( floor(x )+.5, floor(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

                           ( floor(x +.5), floor(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, or slightly larger than, the current point size
     and centered at the point's (x , y ). The total sum of the coverage
                                   w   w
     values of all produced fragments is the window coordinate area of the
     circular point region.  The coverage value for each fragment 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, call fglGet with arguments
     GL_POINT_SIZE_RANGE and GL_POINT_SIZE_GRANULARITY.

NOTES
     The point size specified by fglPointSize is always returned when
     GL_POINT_SIZE is queried.  Clamping and rounding for aliased and
     antialiased points have no effect on the specified value.

     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.

ERRORS
     GL_INVALID_VALUE is generated if size is less than or equal to 0.

     GL_INVALID_OPERATION is generated if fglPointSize is executed between the
     execution of fglBegin and the corresponding execution of fglEnd.

ASSOCIATED GETS
     fglGet with argument GL_POINT_SIZE
     fglGet with argument GL_POINT_SIZE_RANGE
     fglGet with argument GL_POINT_SIZE_GRANULARITY
     fglIsEnabled with argument GL_POINT_SMOOTH



SEE ALSO
     fglEnable