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<STRONG>NAME</STRONG>
<STRONG>glCopyTexSubImage2D</STRONG> - copy a two-dimensional texture
subimage
<STRONG>C</STRONG> <STRONG>SPECIFICATION</STRONG>
void <STRONG>glCopyTexSubImage2D</STRONG>( GLenum <EM>target</EM>,
GLint <EM>level</EM>,
GLint <EM>xoffset</EM>,
GLint <EM>yoffset</EM>,
GLint <EM>x</EM>,
GLint <EM>y</EM>,
GLsizei <EM>width</EM>,
GLsizei <EM>height</EM> )
<STRONG>PARAMETERS</STRONG>
<EM>target</EM> Specifies the target texture. Must be
<STRONG>GL_TEXTURE_2D</STRONG>
<EM>level</EM> Specifies the level-of-detail number. Level 0 is
the base image level. Level <EM>n</EM> is the <EM>n</EM>th mipmap
reduction image.
<EM>xoffset</EM> Specifies a texel offset in the x direction within
the texture array.
<EM>yoffset</EM> Specifies a texel offset in the y direction within
the texture array.
<EM>x</EM>, <EM>y</EM> Specify the window coordinates of the lower left
corner of the rectangular region of pixels to be
copied.
<EM>width</EM> Specifies the width of the texture subimage.
<EM>height</EM> Specifies the height of the texture subimage.
<STRONG>DESCRIPTION</STRONG>
<STRONG>glCopyTexSubImage2D</STRONG> replaces a rectangular portion of a
two-dimensional texture image with pixels from the current
<STRONG>GL_READ_BUFFER</STRONG> (rather than from main memory, as is the case
for <STRONG>glTexSubImage2D</STRONG>).
The screen-aligned pixel rectangle with lower left corner at
(<EM>x</EM>, <EM>y</EM>) and with width <EM>width</EM> and height <EM>height</EM> replaces the
portion of the texture array with x indices <EM>xoffset</EM> through
<EM>xoffset</EM> + <EM>width</EM> - 1, inclusive, and y indices <EM>yoffset</EM>
through <EM>yoffset</EM> + <EM>height</EM> - 1, inclusive, at the mipmap level
specified by <EM>level</EM>.
The pixels in the rectangle are processed exactly as if
<STRONG>glCopyPixels</STRONG> 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.
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.
If any of the pixels within the specified rectangle of the
current <STRONG>GL_READ_BUFFER</STRONG> are outside the read window
associated with the current rendering context, then the
values obtained for those pixels are undefined.
No change is made to the <EM>internalformat</EM>, <EM>width</EM>, <EM>height</EM>, or
<EM>border</EM> parameters of the specified texture array or to texel
values outside the specified subregion.
<STRONG>NOTES</STRONG>
<STRONG>glCopyTexSubImage2D</STRONG> is available only if the GL version is
1.1 or greater.
Texturing has no effect in color index mode.
<STRONG>glPixelStore</STRONG> and <STRONG>glPixelTransfer</STRONG> modes affect texture images
in exactly the way they affect <STRONG>glDrawPixels</STRONG>.
<STRONG>ERRORS</STRONG>
<STRONG>GL_INVALID_ENUM</STRONG> is generated if <EM>target</EM> is not <STRONG>GL_TEXTURE_2D</STRONG>.
<STRONG>GL_INVALID_OPERATION</STRONG> is generated if the texture array has
not been defined by a previous <STRONG>glTexImage2D</STRONG> or
<STRONG>glCopyTexImage2D</STRONG> operation.
<STRONG>GL_INVALID_VALUE</STRONG> is generated if <EM>level</EM> is less than 0.
<STRONG>GL_INVALID_VALUE</STRONG> may be generated if <EM>level</EM> is greater than
log max, where max is the returned value of
<STRONG>GL_MAX_TEXTURE_SIZE</STRONG>.
<STRONG>GL_INVALID_VALUE</STRONG> is generated if <EM>x</EM> < -b or if <EM>y</EM> < -b,
where b is the border width of the texture array.
<STRONG>GL_INVALID_VALUE</STRONG> is generated if xoffset < -b,
(<EM>xoffset</EM> + <EM>width</EM>) > (w - b), <EM>yoffset</EM> < -b, or
(<EM>yoffset</EM> + <EM>height</EM>) > (h - b), where w is the
<STRONG>GL_TEXTURE_WIDTH</STRONG>, h is the <STRONG>GL_TEXTURE_HEIGHT</STRONG>, and b is the
<STRONG>GL_TEXTURE_BORDER</STRONG> of the texture image being modified. Note
that w and h include twice the border width.
<STRONG>GL_INVALID_OPERATION</STRONG> is generated if <STRONG>glCopyTexSubImage2D</STRONG> is
executed between the execution of <STRONG>glBegin</STRONG> and the
corresponding execution of <STRONG>glEnd</STRONG>.
<STRONG>ASSOCIATED</STRONG> <STRONG>GETS</STRONG>
<STRONG>glGetTexImage</STRONG>
<STRONG>glIsEnabled</STRONG> with argument <STRONG>GL_TEXTURE_2D</STRONG>
<STRONG>SEE</STRONG> <STRONG>ALSO</STRONG>
<STRONG>glCopyPixels</STRONG>, <STRONG>glCopyTexImage1D</STRONG>, <STRONG>glCopyTexImage2D</STRONG>,
<STRONG>glCopyTexSubImage1D</STRONG>, <STRONG>glPixelStore</STRONG>, <STRONG>glPixelTransfer</STRONG>,
<STRONG>glTexEnv</STRONG>, <STRONG>glTexGen</STRONG>, <STRONG>glTexImage1D</STRONG>, <STRONG>glTexImage2D</STRONG>,
<STRONG>glTexParameter</STRONG>, <STRONG>glTexSubImage1D</STRONG>, <STRONG>glTexSubImage2D</STRONG>
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