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glLineWidth(3G)		       OpenGL Reference		       glLineWidth(3G)

NAME    [Toc]    [Back]

     glLineWidth - specify the width of	rasterized lines

C SPECIFICATION    [Toc]    [Back]

     void glLineWidth( GLfloat width )

PARAMETERS    [Toc]    [Back]

     width  Specifies the width	of rasterized lines.  The initial value	is 1.

DESCRIPTION    [Toc]    [Back]

     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
     |Wx| > |Wy|, 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

NOTES    [Toc]    [Back]

     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.

									Page 1

glLineWidth(3G)		       OpenGL Reference		       glLineWidth(3G)

ERRORS    [Toc]    [Back]

     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    [Toc]    [Back]

     glGet with	argument GL_LINE_WIDTH
     glGet with	argument GL_ALIASED_LINE_WIDTH_RANGE
     glGet with	argument GL_SMOOTH_LINE_WIDTH_RANGE
     glIsEnabled with argument GL_LINE_SMOOTH

     InfiniteReality systems do	not support antialiased	lines in color-index
     rendering contexts.  (They	are rendered as	ordinary lines instead.)

SEE ALSO    [Toc]    [Back]

     glBlendFunc, glEnable, glHint

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