glLineStipple.3G man page
glLineStipple — specify the line stipple pattern
void glLineStipple(GLint factor, GLushort pattern);
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.
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.
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 % 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 × 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.
GL_INVALID_OPERATION is generated if glLineStipple is executed between the execution of glBegin() and the corresponding execution of glEnd().
glGet() with argument GL_LINE_STIPPLE_PATTERN
glGet() with argument GL_LINE_STIPPLE_REPEAT
glIsEnabled() with argument GL_LINE_STIPPLE
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