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_C_ License Applicability. Except to the extent portions of this file are
_C_ made subject to an alternative license as permitted in the SGI Free
_C_ Software License B, Version 1.1 (the "License"), the contents of this
_C_ file are subject only to the provisions of the License. You may not use
_C_ this file except in compliance with the License. You may obtain a copy
_C_ of the License at Silicon Graphics, Inc., attn: Legal Services, 1600
_C_ Amphitheatre Parkway, Mountain View, CA 94043-1351, or at:
_C_
_C_ http://oss.sgi.com/projects/FreeB
_C_
_C_ Note that, as provided in the License, the Software is distributed on an
_C_ "AS IS" basis, with ALL EXPRESS AND IMPLIED WARRANTIES AND CONDITIONS
_C_ DISCLAIMED, INCLUDING, WITHOUT LIMITATION, ANY IMPLIED WARRANTIES AND
_C_ CONDITIONS OF MERCHANTABILITY, SATISFACTORY QUALITY, FITNESS FOR A
_C_ PARTICULAR PURPOSE, AND NON-INFRINGEMENT.
_C_
_C_ Original Code. The Original Code is: OpenGL Sample Implementation,
_C_ Version 1.2.1, released January 26, 2000, developed by Silicon Graphics,
_C_ Inc. The Original Code is Copyright (c) 1991-2000 Silicon Graphics, Inc.
_C_ Copyright in any portions created by third parties is as indicated
_C_ elsewhere herein. All Rights Reserved.
_C_
_C_ Additional Notice Provisions: The application programming interfaces
_C_ established by SGI in conjunction with the Original Code are The
_C_ OpenGL(R) Graphics System: A Specification (Version 1.2.1), released
_C_ April 1, 1999; The OpenGL(R) Graphics System Utility Library (Version
_C_ 1.3), released November 4, 1998; and OpenGL(R) Graphics with the X
_C_ Window System(R) (Version 1.3), released October 19, 1998. This software
_C_ was created using the OpenGL(R) version 1.2.1 Sample Implementation
_C_ published by SGI, but has not been independently verified as being
_C_ compliant with the OpenGL(R) version 1.2.1 Specification.
_C_
_C_ The first character in this file must be an '_'!
_C_ Anything on a line after _C_ is ignored
_define(_filters,eqn)_C_
_C_ eqn is automatically replaced with neqn for nroff
_header(LineStipple,specify the line stipple pattern)
_names(LineStipple)
.EQ
delim $$
.EN
.SH PARAMETERS
_phead(_param1)
Specifies a multiplier for each bit in the line stipple pattern.
If _param1 is 3,
for example,
each bit in the pattern is used three times
before the next bit in the pattern is used.
_param1 is clamped to the range [1, 256] and defaults to 1.
_phead(_param2)
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.
.SH 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 _param2,
the repeat count _param1,
and an integer stipple counter $s$.
.P
Counter $s$ is reset to 0 whenever _cmnd(Begin) is called,
and before each line segment of a _cmnd(Begin)(_const(LINES))/_cmnd(End)
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
.sp
.ce
_param2 bit $(s ~/~ _eqnparam1) ~roman mod~ 16$
.sp
is 0, otherwise these fragments are sent to the frame buffer.
Bit zero of _param2 is the least significant bit.
.P
Antialiased lines are treated as a sequence of $1 times width$ rectangles
for purposes of stippling.
Whether rectagle $s$ is rasterized or not depends on the fragment rule
described for aliased lines,
counting rectangles rather than groups of fragments.
.P
To enable and disable line stippling, call _cmnd(Enable) and _cmnd(Disable)
with argument _const(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.
.SH ERRORS
_const(INVALID_OPERATION) is generated if _cmnd
is executed between the execution of _cmnd(Begin)
and the corresponding execution of _cmnd(End).
.SH ASSOCIATED GETS
_cmnd(Get) with argument _const(LINE_STIPPLE_PATTERN)
.br
_cmnd(Get) with argument _const(LINE_STIPPLE_REPEAT)
.br
_cmnd(IsEnabled) with argument _const(LINE_STIPPLE)
.SH SEE ALSO
_cmnd(LineWidth),
_cmnd(PolygonStipple)
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