97 lines
3.3 KiB
Plaintext
97 lines
3.3 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 linewidth
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.ds Xs 48623 5 linewidth.gl
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.TH GLLINEWIDTH 3G
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.SH NAME
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.B "glLineWidth
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\- specify the width of rasterized lines
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.SH C SPECIFICATION
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void \f3glLineWidth\fP(
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GLfloat \fIwidth\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'\f2width\fP\ \ 'u
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\f2width\fP
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Specifies the width of rasterized lines.
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The initial value is 1.
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.SH DESCRIPTION
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\%\f3glLineWidth\fP specifies the rasterized width of both aliased and antialiased
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lines.
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Using a line width other than 1 has different effects,
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depending on whether line antialiasing is enabled.
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To enable and disable line antialiasing, call
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\%\f3glEnable\fP and \%\f3glDisable\fP
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with argument \%\f3GL_LINE_SMOOTH\fP. Line antialiasing is initially
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disabled.
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.P
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If line antialiasing is disabled,
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the actual width is determined by rounding the supplied width
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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 line width were 1.)
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If
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$| DELTA x | ~>=~ | DELTA y |$,
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\f2i\fP pixels are filled in each column that is rasterized,
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where \f2i\fP is the rounded value of \f2width\fP.
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Otherwise,
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\f2i\fP pixels are filled in each row that is rasterized.
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.P
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If antialiasing is enabled,
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line rasterization produces a fragment for each pixel square
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that intersects the region lying within the rectangle having width
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equal to the current line width,
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length equal to the actual length of the line,
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and centered on the mathematical line segment.
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The coverage value for each fragment is the window coordinate area
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of the intersection of the rectangular region with the corresponding
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pixel square.
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This value is saved and used in the final rasterization step.
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.P
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Not all widths can be supported when line antialiasing is enabled. If an
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unsupported width is requested, the nearest supported width is used.
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Only width 1 is guaranteed to be supported; others depend on the
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implementation. Likewise, there is a range for aliased line widths as well.
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To query the range of supported widths and the size
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difference between supported widths within the range, call \%\f3glGet\fP
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with arguments \%\f3GL_ALIASED_LINE_WIDTH_RANGE\fP,
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\%\f3GL_SMOOTH_LINE_WIDTH_RANGE\fP, \%\f3GL_SMOOTH_LINE_WIDTH_GRANULARITY\fP.
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.SH NOTES
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The line width specified by \%\f3glLineWidth\fP is always returned when \%\f3GL_LINE_WIDTH\fP
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is queried.
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Clamping and rounding for aliased and antialiased lines have no effect
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on the specified value.
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.P
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Nonantialiased line width may be clamped to an implementation-dependent
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maximum. Call \%\f3glGet\fP with \%\f3GL_ALIASED_LINE_WIDTH_RANGE\fP to
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determine the maximum width.
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.SH ERRORS
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\%\f3GL_INVALID_VALUE\fP is generated if \f2width\fP is less than or equal to 0.
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.P
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\%\f3GL_INVALID_OPERATION\fP is generated if \%\f3glLineWidth\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_LINE_WIDTH\fP
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.br
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\%\f3glGet\fP with argument \%\f3GL_ALIASED_LINE_WIDTH_RANGE\fP
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.br
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\%\f3glGet\fP with argument \%\f3GL_SMOOTH_LINE_WIDTH_RANGE\fP
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.br
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\%\f3glGet\fP with argument \%\f3GL_SMOOTH_LINE_WIDTH_GRANULARITY\fP
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.br
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\%\f3glIsEnabled\fP with argument \%\f3GL_LINE_SMOOTH\fP
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.SH SEE ALSO
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\%\f3glEnable(3G)\fP
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