1991-2006
Silicon Graphics, Inc.
glLineStipple
3G

# glLineStipple

specify the line stipple pattern

## C Specification

                    void glLineStipple
                    GLint factor
                    GLushort pattern

## 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 % 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.

## 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`

## See Also

glLineWidth, glPolygonStipple

## Copyright

Copyright 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.