glLineStipple
The glLineStipple function specifies the line stipple pattern.
void 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.
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
Error Codes
The following is the error code and its condition.
| Error code | Condition |
|---|---|
| GL_INVALID_OPERATION | glLineStipple was called between a call to glBegin and the corresponding call to glEnd. |
Requirements
** Windows NT/2000:** Requires Windows NT 3.5 or later.
** Windows 95/98:** Requires Windows 95 or later. Available as a redistributable for Windows 95.
** Header:** Declared in Gl.h.
** Library:** Use Opengl32.lib.