GLLINESTIPPLE() MachTen Programmer’s Manual GLLINESTIPPLE()

NAME
glLineStipple - specify the line stipple pattern

C SPECIFICATION
void glLineStipple( GLint factor,
GLushort pattern )

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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. fac-
tor 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 frag-
ment 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 rec-
tagle $s$ 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. Ini-
tially, line stippling is disabled.

ERRORS
GL_INVALID_OPERATION is generated if glLineStipple is exe-
cuted between the execution of glBegin and the correspond-
ing 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