glLineWidth - specify the width of rasterized lines
void glLineWidth(
GLfloat 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(3)
glLineWidth(3G)
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