_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
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_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_ $Date$ $Revision$
_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(RasterPos,specify the raster position for pixel operations)
_names(RasterPos,[2-4][sifd])
.EQ
delim $$
.EN
.SH PARAMETERS
_phead(_param1 _param2 _param3 _param4)
Specify the $x$, $y$, $z$, and $w$ object coordinates
(if present)
for the raster position.
_names(RasterPos,[2-4][sifd]v)
.SH PARAMETERS
_phead(_param1)
Specifies a pointer to an array of two,
three,
or four elements,
specifying $x$, $y$, $z$, and $w$ coordinates, respectively.
.SH DESCRIPTION
The GL maintains a 3D position in window coordinates.
This position,
called the raster position,
is used to position pixel and bitmap write operations. It is
maintained with subpixel accuracy.
See _cmnd(Bitmap), _cmnd(DrawPixels), and _cmnd(CopyPixels).
.P
The current raster position consists of three window coordinates
($x$, $y$, $z$),
a clip coordinate value ($w$),
an eye coordinate distance,
a valid bit,
and associated color data and texture coordinates.
The $w$ coordinate is a clip coordinate,
because $w$ is not projected to window coordinates.
_cmnd(RasterPos4) specifies object coordinates $x$, $y$, $z$, and $w$
explicitly.
_cmnd(RasterPos3) specifies object coordinate $x$, $y$, and $z$ explicitly,
while $w$ is implicitly set to 1.
_cmnd(RasterPos2) uses the argument values for $x$ and $y$ while
implicitly setting $z$ and $w$ to 0 and 1.  
.P
The object coordinates presented by _cmnd are treated just like those
of a _cmnd(Vertex) command:
They are transformed by the current modelview and projection matrices
and passed to the clipping stage.
If the vertex is not culled,
then it is projected and scaled to window coordinates,
which become the new current raster position,
and the _const(CURRENT_RASTER_POSITION_VALID) flag is set.
If the vertex 
.I is
culled,
then the valid bit is cleared and the current raster position
and associated color and texture coordinates are undefined.
.P
The current raster position also includes some associated color data
and texture coordinates.
If lighting is enabled,
then _const(CURRENT_RASTER_COLOR)
(in RGBA mode)
or _const(CURRENT_RASTER_INDEX)
(in color index mode)
is set to the color produced by the lighting calculation
(see _cmnd(Light), _cmnd(LightModel), and 
.br
_cmnd(ShadeModel)).
If lighting is disabled, 
current color
(in RGBA mode, state variable _const(CURRENT_COLOR))
or color index
(in color index mode, state variable _const(CURRENT_INDEX))
is used to update the current raster color.
.P
Likewise,
_const(CURRENT_RASTER_TEXTURE_COORDS) is updated as a function
of _const(CURRENT_TEXTURE_COORDS),
based on the texture matrix and the texture generation functions
(see _cmnd(TexGen)).
Finally,
the distance from the origin of the eye coordinate system to the
vertex as transformed by only the modelview matrix replaces
_const(CURRENT_RASTER_DISTANCE).
.P
Initially, the current raster position is (0, 0, 0, 1),
the current raster distance is 0,
the valid bit is set,
the associated RGBA color is (1, 1, 1, 1),
the associated color index is 1,
and the associated texture coordinates are (0, 0, 0, 1).
In RGBA mode,
_const(CURRENT_RASTER_INDEX) is always 1;
in color index mode,
the current raster RGBA color always maintains its initial value.
.SH NOTES
The raster position is modified both by _cmnd and by _cmnd(Bitmap). 
.P
When the raster position coordinates are invalid,
drawing commands that are based on the raster position are
ignored (that is, they do not result in changes to GL state).
.P
Calling _cmnd(DrawElements), or _cmnd(DrawRangeElements) may leave the
current color or index indeterminate.
If _cmnd is executed while the current color or index is indeterminate, the
current raster color or current raster index remains indeterminate.
.P
To set a valid raster position outside the viewport, first set a valid
raster position, then call _cmnd(Bitmap) with NULL as the \f2bitmap\fP
parameter.
.P
When the _arbstring(imaging) extension is supported, there are distinct
raster texture coordinates for each texture unit. Each texture unit's
current ratster texture coordinates are updated by _cmnd.
.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(CURRENT_RASTER_POSITION)
.br
_cmnd(Get) with argument _const(CURRENT_RASTER_POSITION_VALID)
.br
_cmnd(Get) with argument _const(CURRENT_RASTER_DISTANCE)
.br
_cmnd(Get) with argument _const(CURRENT_RASTER_COLOR)
.br
_cmnd(Get) with argument _const(CURRENT_RASTER_INDEX)
.br
_cmnd(Get) with argument _const(CURRENT_RASTER_TEXTURE_COORDS)
.SH SEE ALSO
_cmnd(Bitmap),
_cmnd(CopyPixels),
_cmnd(DrawArrays),
_cmnd(DrawElements),
_cmnd(DrawRangeElements),
_cmnd(DrawPixels),
_cmnd(TexCoord),
_cmnd(TexGen),
_cmnd(Vertex)
