GLLINEWIDTH(3gl)GLLINEWIDTH(3gl)NAMEglLineWidth - 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.
DESCRIPTIONglLineWidth 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 argu‐
ment 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 seg‐
ment. 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 rasteriza‐
tion 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 imple‐
mentation. To query the range of supported widths and the size differ‐
ence between supported widths within the range, call glGet with argu‐
ments GL_LINE_WIDTH_RANGE and GL_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. Although this maximum cannot be queried, it must be no less
than the maximum value for antialiased lines, rounded to the nearest
integer value.
ERRORS
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.
ASSOCIATED GETS
glGet with argument GL_LINE_WIDTH
glGet with argument GL_LINE_WIDTH_RANGE
glGet with argument GL_LINE_WIDTH_GRANULARITY
glIsEnabled with argument GL_LINE_SMOOTH
SEE ALSO
glEnable
15 Mar 97 GLLINEWIDTH(3gl)
