NAME

glLineWidth - specify the width of rasterized lines

C SPECIFICATION

void ggllLLiinneeWWiiddtthh( GLfloat _w_i_d_t_h )

        

delim $$

PARAMETERS

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

DESCRIPTION

ggllLLiinneeWWiiddtthh 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 ggllEEnnaabbllee and ggllDDiissaabbllee with argument GGLL__LLIINNEE__SSMMOOOOTTHH. 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 _w_i_d_t_h. 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 ggllGGeett with arguments GGLL__AALLIIAASSEEDD__LLIINNEE__WWIIDDTTHH__RRAANNGGEE, GGLL__SSMMOOOOTTHH__LLIINNEE__WWIIDDTTHH__RRAANNGGEE, GGLL__SSMMOOOOTTHH__LLIINNEE__WWIIDDTTHH__GGRRAANNUULLAARRIITTYY.

NOTES

The line width specified by ggllLLiinneeWWiiddtthh is always returned when GGLL__LLIINNEE__WWIIDDTTHH 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 ggllGGeett with GGLL__AALLIIAASSEEDD__LLIINNEE__WWIIDDTTHH__RRAANNGGEE to determine the maximum width.

ERRORS

GGLL__IINNVVAALLIIDD__VVAALLUUEE is generated if _w_i_d_t_h is less than or equal to 0.

GGLL__IINNVVAALLIIDD__OOPPEERRAATTIIOONN is generated if ggllLLiinneeWWiiddtthh is executed between the execution of ggllBBeeggiinn and the corresponding execution of ggllEEnndd.

ASSOCIATED GETS

ggllGGeett with argument GGLL__LLIINNEE__WWIIDDTTHH
ggllGGeett with argument GGLL__AALLIIAASSEEDD__LLIINNEE__WWIIDDTTHH__RRAANNGGEE
ggllGGeett with argument GGLL__SSMMOOOOTTHH__LLIINNEE__WWIIDDTTHH__RRAANNGGEE
ggllGGeett with argument GGLL__SSMMOOOOTTHH__LLIINNEE__WWIIDDTTHH__GGRRAANNUULLAARRIITTYY
ggllIIssEEnnaabblleedd with argument GGLL__LLIINNEE__SSMMOOOOTTHH

SEE ALSO

ggllEEnnaabbllee((33GG))