glLineWidth man page on RedHat
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GLLINEWIDTH(3G) OpenGL Manual 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 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 Δ x >= Δ
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, and
GL_SMOOTH_LINE_WIDTH_GRANULARITY.
NOTES
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.
In OpenGL 1.2, the tokens GL_LINE_WIDTH_RANGE and
GL_LINE_WIDTH_GRANULARITY were replaced by GL_ALIASED_LINE_WIDTH_RANGE,
GL_SMOOTH_LINE_WIDTH_RANGE, and GL_SMOOTH_LINE_WIDTH_GRANULARITY. The
old names are retained for backward compatibility, but should not be
used in new code.
ERRORS
GL_INVALID_VALUE is generated if width is less than or equal to 0.
ASSOCIATED GETS
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
SEE ALSO
glEnable()
COPYRIGHT
Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed
under the SGI Free Software B License. For details, see
http://oss.sgi.com/projects/FreeB/.
AUTHORS
opengl.org
opengl.org 03/16/2013 GLLINEWIDTH(3G)
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