GLLINESTIPPLE

Section: Misc. Reference Manual Pages (3G)
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NAME

glLineStipple - specify the line stipple pattern

C SPECIFICATION

void glLineStipple( GLint factor,


                      GLushort pattern )

delim $$

PARAMETERS

factor: Specifies a multiplier for each bit in the line stipple pattern. If factor is 3, for example, each bit in the pattern is used three times before the next bit in the pattern is used. factor is clamped to the range [1, 256] and defaults to 1.
pattern: Specifies 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; the default pattern is all 1's.

DESCRIPTION

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 0 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 $(s ~/~ "factor") ~roman mod~ 16$

is 0, otherwise these fragments are sent to the frame buffer. Bit zero of pattern is the least significant bit.

Antialiased lines are treated as a sequence of $1 times width$ rectangles for purposes of stippling. Whether rectangle $s$ is rasterized or not depends on the fragment rule described for aliased lines, counting rectangles rather than groups of fragments.

To enable and disable line stippling, call 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 1's. Initially, line stippling is disabled.

ERRORS

GL_INVALID_OPERATION is generated if glLineStipple is executed between the execution of glBegin and the corresponding execution of glEnd.

ASSOCIATED GETS

glGet with argument GL_LINE_STIPPLE_PATTERN
glGet with argument GL_LINE_STIPPLE_REPEAT
glIsEnabled with argument GL_LINE_STIPPLE