glLineStipple function

The glLineStipple function specifies the line stipple pattern.

Syntax

void WINAPI glLineStipple(
   GLint    factor,
   GLushort pattern
);

Parameters

factor

A multiplier for each bit in the line stipple pattern. If factor is 3, for example, each bit in the pattern will be used three times before the next bit in the pattern is used. The factor parameter is clamped to the range [1, 256] and defaults to one.

pattern

A 16-bit integer whose bit pattern determines which fragments of a line will be drawn when the line is rasterized. Bit zero is used first, and the default pattern is all ones.

Return value

This function does not return a value.

Error codes

The following error code can be retrieved by the glGetError function.

Remarks

The glLineStipple function specifies the line stipple pattern. Line stippling masks out certain fragments produced by rasterization; those fragments will not be drawn. The masking is achieved by using three parameters: the 16-bit line stipple pattern pattern, the repeat count factor, and an integer stipple counter s.

Counter s is reset to zero whenever glBegin is called, and before each line segment of a glBegin(GL_LINES)/glEnd sequence is generated. It is incremented after each fragment of a unit width aliased line segment is generated, or after each i fragments of an i width line segment are generated. The i fragments associated with count s are masked out if pattern bit (s / factor) mod 16 is zero. Otherwise these fragments are sent to the framebuffer. Bit zero of pattern is the least significant bit.

Antialiased lines are treated as a sequence of 1xwidth rectangles for purposes of stippling. Rectangle s is rasterized or not based on the fragment rule described for aliased lines; it counts rectangles rather than groups of fragments.

Line stippling is enabled or disabled using glEnable and glDisable with argument GL_LINE_STIPPLE. When enabled, the line stipple pattern is applied as described above. When disabled, it is as if the pattern were all ones. Initially, line stippling is disabled.

The following functions retrieve information related to glLineStipple:

glGet with argument GL_LINE_STIPPLE_PATTERN

glGet with argument GL_LINE_STIPPLE_REPEAT

glIsEnabled with argument GL_LINE_STIPPLE

Requirements

See also

glBegin

glEnd

glLineWidth

glPolygonStipple