129 lines
4.3 KiB
Plaintext
129 lines
4.3 KiB
Plaintext
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'\" e
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'\"! eqn | mmdoc
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'\"macro stdmacro
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.ds Vn Version 1.2
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.ds Dt 24 September 1999
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.ds Re Release 1.2.1
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.ds Dp Jan 14 18:30
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.ds Dm 01 pointsize
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.ds Xs 46128 6 pointsize.gl
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.TH GLPOINTSIZE 3G
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.SH NAME
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.B "glPointSize
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\- specify the diameter of rasterized points
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.SH C SPECIFICATION
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void \f3glPointSize\fP(
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GLfloat \fIsize\fP )
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.nf
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.fi
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.EQ
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delim $$
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.EN
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.SH PARAMETERS
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.TP \w'\f2size\fP\ \ 'u
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\f2size\fP
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Specifies the diameter of rasterized points.
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The initial value is 1.
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.SH DESCRIPTION
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\%\f3glPointSize\fP specifies the rasterized diameter of both aliased and antialiased
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points.
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Using a point size other than 1 has different effects,
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depending on whether point antialiasing is enabled.
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To enable and disable point antialiasing, call
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\%\f3glEnable\fP and \%\f3glDisable\fP
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with argument \%\f3GL_POINT_SMOOTH\fP. Point antialiasing is initially disabled.
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.P
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If point antialiasing is disabled,
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the actual size is determined by rounding the supplied size
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to the nearest integer.
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(If the rounding results in the value 0,
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it is as if the point size were 1.)
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If the rounded size is odd,
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then the center point
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($ x $, $ y $)
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of the pixel fragment that represents the point is computed as
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.sp
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.ce
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( $ \(lf ~ x sub w ~ \(rf ~+~ .5 $, $ \(lf ~ y sub w ~ \(rf ~+~ .5 $)
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.sp
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where $w$ subscripts indicate window coordinates.
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All pixels that lie within the square grid of the rounded size centered at
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($ x $, $ y $)
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make up the fragment.
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If the size is even,
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the center point is
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.sp
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.ce
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( $ \(lf ~ x sub w ~+~ .5 ~ \(rf$, $ \(lf ~ y sub w ~+~ .5 ~ \(rf $)
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.sp
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and the rasterized fragment's centers are the half-integer window coordinates
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within the square of the rounded size centered at
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($ x $, $ y $).
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All pixel fragments produced in rasterizing a nonantialiased point are
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assigned the same associated data,
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that of the vertex corresponding to the point.
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.P
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If antialiasing is enabled,
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then point rasterization produces a fragment for each pixel square
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that intersects the region lying within the circle having diameter
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equal to the current point size and centered at the point's
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($ x sub w $, $ y sub w $).
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The coverage value for each fragment is the window coordinate area
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of the intersection of the circular region with the corresponding pixel square.
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This value is saved and used in the final rasterization step.
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The data associated with each fragment is the data associated with
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the point being rasterized.
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.P
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Not all sizes are supported when point antialiasing is enabled.
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If an unsupported size is requested,
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the nearest supported size is used.
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Only size 1 is guaranteed to be supported;
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others depend on the implementation.
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To query the range of supported sizes and the size difference between
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supported sizes within the range, call
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\%\f3glGet\fP with arguments
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\%\f3GL_SMOOTH_POINT_SIZE_RANGE\fP and
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\%\f3GL_SMOOTH_POINT_SIZE_GRANULARITY\fP.
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For aliased points, query the supported ranges and granularity with
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\%\f3glGet\fP with arguments
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\%\f3GL_ALIASED_POINT_SIZE_RANGE\fP and
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\%\f3GL_ALIASED_POINT_SIZE_GRANULARITY\fP.
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.SH NOTES
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The point size specified by \%\f3glPointSize\fP is always returned when \%\f3GL_POINT_SIZE\fP
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is queried.
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Clamping and rounding for aliased and antialiased points have no effect
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on the specified value.
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.P
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A non-antialiased point size may be clamped to an implementation-dependent
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maximum.
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Although this maximum cannot be queried,
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it must be no less than the maximum value for antialiased points,
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rounded to the nearest integer value.
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.P
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\%\f3GL_POINT_SIZE_RANGE\fP and \%\f3GL_POINT_SIZE_GRANULARITY\fP are
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deprecated in GL versions 1.2 and greater. Their functionality has been
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replaced by \%\f3GL_SMOOTH_POINT_SIZE_RANGE\fP and
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\%\f3GL_SMOOTH_POINT_SIZE_GRANULARITY\fP.
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.SH ERRORS
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\%\f3GL_INVALID_VALUE\fP is generated if \f2size\fP is less than or equal to 0.
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.P
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\%\f3GL_INVALID_OPERATION\fP is generated if \%\f3glPointSize\fP
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is executed between the execution of \%\f3glBegin\fP
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and the corresponding execution of \%\f3glEnd\fP.
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.SH ASSOCIATED GETS
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\%\f3glGet\fP with argument \%\f3GL_POINT_SIZE\fP
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.br
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\%\f3glGet\fP with argument \%\f3GL_ALIASED_POINT_SIZE_RANGE\fP
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.br
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\%\f3glGet\fP with argument \%\f3GL_ALIASED_POINT_SIZE_GRANULARITY\fP
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.br
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\%\f3glGet\fP with argument \%\f3GL_SMOOTH_POINT_SIZE_RANGE\fP
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.br
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\%\f3glGet\fP with argument \%\f3GL_SMOOTH_POINT_SIZE_GRANULARITY\fP
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.br
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\%\f3glIsEnabled\fP with argument \%\f3GL_POINT_SMOOTH\fP
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.SH SEE ALSO
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\%\f3glEnable(3G)\fP
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