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Manpage of GLPOINTSIZE

GLPOINTSIZE

Index
 

NAME

glPointSize - specify the diameter of rasterized points

 

C SPECIFICATION

void f3glPointSizefP( GLfloat fIsizefP )


delim $$  

PARAMETERS

f2sizefP
Specifies the diameter of rasterized points. The initial value is 1.
 

DESCRIPTION

%f3glPointSizefP 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 %f3glEnablefP and %f3glDisablefP with argument %f3GL_POINT_SMOOTHfP. 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

( $ (lf ~ x sub w ~ (rf ~+~ .5 $, $ (lf ~ y sub w ~ (rf ~+~ .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

( $ (lf ~ x sub w ~+~ .5 ~ (rf$, $ (lf ~ y sub w ~+~ .5 ~ (rf $)

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 %f3glGetfP with arguments %f3GL_SMOOTH_POINT_SIZE_RANGEfP and %f3GL_SMOOTH_POINT_SIZE_GRANULARITYfP. For aliased points, query the supported ranges and granularity with %f3glGetfP with arguments %f3GL_ALIASED_POINT_SIZE_RANGEfP and %f3GL_ALIASED_POINT_SIZE_GRANULARITYfP.  

NOTES

The point size specified by %f3glPointSizefP is always returned when %f3GL_POINT_SIZEfP 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. %f3GL_POINT_SIZE_RANGEfP and %f3GL_POINT_SIZE_GRANULARITYfP are deprecated in GL versions 1.2 and greater. Their functionality has been replaced by %f3GL_SMOOTH_POINT_SIZE_RANGEfP and %f3GL_SMOOTH_POINT_SIZE_GRANULARITYfP.  

ERRORS

%f3GL_INVALID_VALUEfP is generated if f2sizefP is less than or equal to 0. %f3GL_INVALID_OPERATIONfP is generated if %f3glPointSizefP is executed between the execution of %f3glBeginfP and the corresponding execution of %f3glEndfP.  

ASSOCIATED GETS

%f3glGetfP with argument %f3GL_POINT_SIZEfP
%f3glGetfP with argument %f3GL_ALIASED_POINT_SIZE_RANGEfP
%f3glGetfP with argument %f3GL_ALIASED_POINT_SIZE_GRANULARITYfP
%f3glGetfP with argument %f3GL_SMOOTH_POINT_SIZE_RANGEfP
%f3glGetfP with argument %f3GL_SMOOTH_POINT_SIZE_GRANULARITYfP
%f3glIsEnabledfP with argument %f3GL_POINT_SMOOTHfP  

SEE ALSO

%f3glEnable(3G)fP


 

Index

NAME
C SPECIFICATION
PARAMETERS
DESCRIPTION
NOTES
ERRORS
ASSOCIATED GETS
SEE ALSO