_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,tbl|eqn)_C_
_C_      eqn is automatically replaced with neqn for nroff
_header(CopyTexSubImage2D,copy a two-dimensional texture subimage)
_names(CopyTexSubImage2D)
.EQ
delim $$
.EN
.SH PARAMETERS
_phead(_param1)
Specifies the target texture.
Must be _const(TEXTURE_2D).
_phead(_param2)
Specifies the level-of-detail number.
Level 0 is the base image level.
Level \f2n\fP is the \f2n\fPth mipmap reduction image.
_phead(_param3)
Specifies a texel offset in the x direction within the texture array.
_phead(_param4)
Specifies a texel offset in the y direction within the texture array.
_phead(_param5 _param6)
Specify the window coordinates of the lower left corner
of the rectangular region of pixels to be copied.
_phead(_param7)
Specifies the width of the texture subimage.
_phead(_param8)
Specifies the height of the texture subimage.
.SH DESCRIPTION
_cmnd replaces a rectangular portion of a two-dimensional
texture image with pixels from the current _const(READ_BUFFER) (rather
than from main memory, as is the case for _cmnd(TexSubImage2D)).
.P
The screen-aligned pixel rectangle with lower left corner at
(_param5,\ _param6) and with
width _param7 and height _param8 replaces the portion of the
texture array with x indices _param3 through _param3$~+~$_param7$~-~$1,
inclusive, and y indices _param4 through _param4$~+~$_param8$~-~$1,
inclusive, at the mipmap level specified by _param2.
.P
The pixels in the rectangle are processed exactly as if
_cmnd(CopyPixels) had been called, but the process stops just before
final conversion.
At this point, all pixel component values are clamped to the range [0,\ 1]
and then converted to the texture's internal format for storage in the texel
array.
.P
The destination rectangle in the texture array may not include any texels
outside the texture array as it was originally specified.
It is not an error to specify a subtexture with zero width or height, but
such a specification has no effect.
.P
If any of the pixels within the specified rectangle of the current
_const(READ_BUFFER) are outside the read window associated with the current
rendering context, then the values obtained for those pixels are undefined.
.P
No change is made to the \f2internalformat\fP, \f2width\fP,
\f2height\fP, or \f2border\fP parameters of the specified texture
array or to texel values outside the specified subregion.
.SH NOTES
_cmnd is available only if the GL version is 1.1 or greater. 
.P
Texturing has no effect in color index mode.
.P
_cmnd(PixelStore) and _cmnd(PixelTransfer) modes affect texture images
in exactly the way they affect _cmnd(DrawPixels).
.P
When the _arbstring(imaging) extension is supported, the RGBA components
read from the framebuffer may be processed by the imaging pipeline.  See
_cmnd(TexImage1D) for specific details.
.SH ERRORS
_const(INVALID_ENUM) is generated if _param1 is not _const(TEXTURE_2D). 
.P
_const(INVALID_OPERATION) is generated if the texture array has not
been defined by a previous _cmnd(TexImage2D) or _cmnd(CopyTexImage2D) operation.
.P
_const(INVALID_VALUE) is generated if _param2 is less than 0.
.P 
_const(INVALID_VALUE) may be generated if _param2 is greater
than $log sub 2 max$,
where $max$ is the returned value of _const(MAX_TEXTURE_SIZE).
.P
_const(INVALID_VALUE) is generated if _param5$ ~<~ ~-b$ or if
_param6$ ~<~ ~-b$, 
where $b$ is the border width of the texture array.
.P
_const(INVALID_VALUE) is generated if $_eqnparam3 ~<~ -b$,
(_param3$~+~$_param7)$~>~(w ~-~b)$, 
_param4$~<~ ~-b$, or 
(_param4$~+~$_param8)$~>~(h ~-~b)$,
where $w$ is the _const(TEXTURE_WIDTH), 
$h$ is the  _const(TEXTURE_HEIGHT), 
and $b$ is the _const(TEXTURE_BORDER)
of the texture image being modified.
Note that $w$ and $h$
include twice the border width.
.P
_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(GetTexImage)
.br
_cmnd(IsEnabled) with argument _const(TEXTURE_2D)
.SH SEE ALSO
_cmnd(CopyPixels),
_cmnd(CopyTexImage1D),
_cmnd(CopyTexImage2D),
_cmnd(CopyTexSubImage1D),
_cmnd(CopyTexSubImage3D),
_cmnd(PixelStore),
_cmnd(PixelTransfer),
_cmnd(ReadBuffer),
_cmnd(TexEnv),
_cmnd(TexGen),
_cmnd(TexImage1D),
_cmnd(TexImage2D),
_cmnd(TexImage3D),
_cmnd(TexParameter),
_cmnd(TexSubImage1D),
_cmnd(TexSubImage2D),
_cmnd(TexSubImage3D)
