glLineWidth(3G) OpenGL Reference glLineWidth(3G)
NAME
glLineWidth - specify the width of rasterized lines
C SPECIFICATION
void glLineWidth( GLfloat width )
PARAMETERS
width Specifies the width of rasterized lines. The initial value is 1.
DESCRIPTION
glLineWidth specifies the rasterized width of both aliased and
antialiased lines. Using a line width other than 1 has different
effects, depending on whether line antialiasing is enabled. To enable
and disable line antialiasing, call glEnable and glDisable with argument
GLLINESMOOTH. Line antialiasing is initially disabled.
If line antialiasing is disabled, the actual width is determined by
rounding the supplied width to the nearest integer. (If the rounding
results in the value 0, it is as if the line width were 1.) If
| DELTA x | >= | DELTA y |,
i pixels are filled in each column that is rasterized, where i is the
rounded value of width. Otherwise, i pixels are filled in each row that
is rasterized.
If antialiasing is enabled, line rasterization produces a fragment for
each pixel square that intersects the region lying within the rectangle
having width equal to the current line width, length equal to the actual
length of the line, and centered on the mathematical line segment. The
coverage value for each fragment is the window coordinate area of the
intersection of the rectangular region with the corresponding pixel
square. This value is saved and used in the final rasterization step.
Not all widths can be supported when line antialiasing is enabled. If an
unsupported width is requested, the nearest supported width is used.
Only width 1 is guaranteed to be supported; others depend on the
implementation. To query the range of supported widths and the size
difference between supported widths within the range, call glGet with
arguments GLLINEWIDTHRANGE and GLLINEWIDTHGRANULARITY.
NOTES
The line width specified by glLineWidth is always returned when
GLLINEWIDTH is queried. Clamping and rounding for aliased and
antialiased lines have no effect on the specified value.
Nonantialiased line width 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 lines, rounded to the nearest
integer value.
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glLineWidth(3G) OpenGL Reference glLineWidth(3G)
ERRORS
GLINVALIDVALUE is generated if width is less than or equal to 0.
GLINVALIDOPERATION is generated if glLineWidth is executed between the
execution of glBegin and the corresponding execution of glEnd.
ASSOCIATED GETS
glGet with argument GLLINEWIDTH
glGet with argument GLLINEWIDTHRANGE
glGet with argument GLLINEWIDTHGRANULARITY
glIsEnabled with argument GLLINESMOOTH
MACHINE DEPENDENCIES
InfiniteReality systems do not support antialiased lines in color-index
rendering contexts. (They are rendered as ordinary lines instead.)
SEE ALSO
glBlendFunc, glEnable, glHint
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