NAME

glPointSize - specify the diameter of rasterized points

C SPECIFICATION

void ggllPPooiinnttSSiizzee( GLfloat _s_i_z_e )

        

delim $$

PARAMETERS

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

DESCRIPTION

ggllPPooiinnttSSiizzee 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 ggllEEnnaabbllee and ggllDDiissaabbllee with argument GGLL__PPOOIINNTT__SSMMOOOOTTHH. 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 sub w ~ ~+~ .5 $, $ ~ y sub 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 sub w ~+~ .5 ~ $, $ ~ y sub 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 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 sub w $, $ y sub 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 ggllGGeett with arguments GGLL__SSMMOOOOTTHH__PPOOIINNTT__SSIIZZEE__RRAANNGGEE and GGLL__SSMMOOOOTTHH__PPOOIINNTT__SSIIZZEE__GGRRAANNUULLAARRIITTYY. For aliased points, query the supported ranges and granularity with ggllGGeett with arguments GGLL__AALLIIAASSEEDD__PPOOIINNTT__SSIIZZEE__RRAANNGGEE and GGLL__AALLIIAASSEEDD__PPOOIINNTT__SSIIZZEE__GGRRAANNUULLAARRIITTYY.

NOTES

The point size specified by ggllPPooiinnttSSiizzee is always returned when GGLL__PPOOIINNTT__SSIIZZEE 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.

GGLL__PPOOIINNTT__SSIIZZEE__RRAANNGGEE and GGLL__PPOOIINNTT__SSIIZZEE__GGRRAANNUULLAARRIITTYY are deprecated in GL versions 1.2 and greater. Their functionality has been replaced by GGLL__SSMMOOOOTTHH__PPOOIINNTT__SSIIZZEE__RRAANNGGEE and GGLL__SSMMOOOOTTHH__PPOOIINNTT__SSIIZZEE__GGRRAANNUULLAARRIITTYY.

ERRORS

GGLL__IINNVVAALLIIDD__VVAALLUUEE is generated if _s_i_z_e is less than or equal to 0.

GGLL__IINNVVAALLIIDD__OOPPEERRAATTIIOONN is generated if ggllPPooiinnttSSiizzee is executed between the execution of ggllBBeeggiinn and the corresponding execution of ggllEEnndd.

ASSOCIATED GETS

ggllGGeett with argument GGLL__PPOOIINNTT__SSIIZZEE
ggllGGeett with argument GGLL__AALLIIAASSEEDD__PPOOIINNTT__SSIIZZEE__RRAANNGGEE
ggllGGeett with argument GGLL__AALLIIAASSEEDD__PPOOIINNTT__SSIIZZEE__GGRRAANNUULLAARRIITTYY
ggllGGeett with argument GGLL__SSMMOOOOTTHH__PPOOIINNTT__SSIIZZEE__RRAANNGGEE
ggllGGeett with argument GGLL__SSMMOOOOTTHH__PPOOIINNTT__SSIIZZEE__GGRRAANNUULLAARRIITTYY
ggllIIssEEnnaabblleedd with argument GGLL__PPOOIINNTT__SSMMOOOOTTHH

SEE ALSO

ggllEEnnaabbllee((33GG))