GLLINEWIDTH(3G) UNIX Programmer's Manual GLLINEWIDTH(3G)
glLineWidth - specify the width of rasterized lines
void glLineWidth( GLfloat width )
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 deter-
mined 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 |_\_x| ≥ |_\_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 correspond-
ing 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
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GLLINEWIDTH(3G) UNIX Programmer's Manual GLLINEWIDTH(3G)
aliased and antialiased lines have no effect on the speci-
fied 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 exe-
cution 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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