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Table of Contents
glLineWidth - specify the width of rasterized lines
void
glLineWidth( GLfloat width )
eqn not supported
- width
- Specifies the width of rasterized lines.
The initial value is 1.
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 GL_LINE_SMOOTH. 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. Likewise, there is
a range for aliased line widths as well. To query the range of supported
widths and the size difference between supported widths within the range,
call glGet with arguments GL_ALIASED_LINE_WIDTH_RANGE, GL_SMOOTH_LINE_WIDTH_RANGE,
GL_SMOOTH_LINE_WIDTH_GRANULARITY.
The line width specified by glLineWidth
is always returned when GL_LINE_WIDTH 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. Call glGet with GL_ALIASED_LINE_WIDTH_RANGE to determine the maximum
width.
GL_INVALID_VALUE is generated if width is less than or equal
to 0.
GL_INVALID_OPERATION is generated if glLineWidth is executed between
the execution of glBegin and the corresponding execution of glEnd.
glGet with argument GL_LINE_WIDTH
glGet with argument GL_ALIASED_LINE_WIDTH_RANGE
glGet with argument GL_SMOOTH_LINE_WIDTH_RANGE
glGet with argument GL_SMOOTH_LINE_WIDTH_GRANULARITY
glIsEnabled with argument GL_LINE_SMOOTH
glEnable(3G)
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