glCopyTexSubImage2DEXT(3G)     OpenGL Reference	    glCopyTexSubImage2DEXT(3G)



NAME
     glCopyTexSubImage2DEXT - copy pixels into a 2D texture subimage


C SPECIFICATION
     void glCopyTexSubImage2DEXT( GLenum target,
				  GLint	level,
				  GLint	xoffset,
				  GLint	yoffset,
				  GLint	x,
				  GLint	y,
				  GLsizei width,
				  GLsizei height )


PARAMETERS
     target   The target texture.  Must	be GL_TEXTURE_2D or
	      GL_DETAIL_TEXTURE_2D_SGIS.

     level    The level-of-detail number.  Level 0 is the base image level.
	      Level n is the nth mipmap	reduction image.

     xoffset  A	texel offset in	the x direction	within the texture array.

     yoffset  A	texel offset in	the y direction	within the texture array.

     x	      The x coordinate of the lower-left corner	of the pixel rectangle
	      to be transferred	to the texture array.

     y	      The y coordinate of the lower-left corner	of the pixel rectangle
	      to be transferred	to the texture array.

     width    The width	of the texture subimage.

     height   The height of the	texture	subimage.

DESCRIPTION
     glCopyTexSubImage2DEXT replaces a rectangular portion of a	two-
     dimensional texture image with pixels from	the current GL_READ_BUFFER
     (rather than from main memory, as is the case for glTexSubImage2DEXT).

     The screen-aligned	pixel rectangle	with lower-left	corner at (x, y)
     having width width	and height height replaces the portion of the texture
     array with	x indices xoffset through xoffset+width-1, inclusive, and y
     indices yoffset through yoffset+height-1, inclusive, at the mipmap	level
     specified by level.  (But see the paragraph about GL_INTERLACE_SGIX
     below).

     The pixels	in the rectangle are processed exactly as if glCopyPixels 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



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glCopyTexSubImage2DEXT(3G)     OpenGL Reference	    glCopyTexSubImage2DEXT(3G)



     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
     GL_READ_BUFFER are	outside	the read window	associated with	the current
     rendering context,	then the values	obtained for those pixels are
     undefined.

     When GL_INTERLACE_SGIX is enabled,	successive rows	of source pixels are
     written to	every other row	in the texture subimage, rather	than to	every
     successive	row.  That is, row j or	the source image is written to row
     yoffset+2j	of the destination texture, while rows
     (yoffset+1,yoffset+3,...) are not modified.  A complete video frame may
     be	assembled in texture memory by invoking	glCopyTexSubImage2DEXT on two
     consecutive video fields, with yoffset values that	differ by one.

NOTES
     glCopyTexSubImage2DEXT is part of the EXT_copy_texture extension, and
     GL_INTERLACE_SGIX is part of the SGIX_interlace extension.	 See glIntro
     for more information about	using extensions.

ERRORS
     GL_INVALID_ENUM is	generated when target is not one of the	allowable
     values.

     GL_INVALID_VALUE is generated if level is less than zero or greater than
     log2(max),	where max is the returned value	of GL_MAX_TEXTURE_SIZE.

     GL_INVALID_VALUE is generated if xoffset<-TEXTURE_BORDER,
     (xoffset+width)>(TEXTURE_WIDTH-TEXTURE_BORDER), yoffset<-TEXTURE_BORDER,
     or	(yoffset+interlacexheight)>(TEXTURE_HEIGHT-TEXTURE_BORDER).  Where
     TEXTURE_WIDTH, TEXTURE_HEIGHT, and	TEXTURE_BORDER are the state values of
     the texture image being modified, and interlace is	1 if GL_INTERLACE_SGIX
     is	disabled and 2 otherwise.  Note	that TEXTURE_WIDTH and TEXTURE_HEIGHT
     include twice the border width.

     GL_INVALID_VALUE is generated if width or height is negative.

     GL_INVALID_OPERATION is generated when the	texture	array has not been
     defined by	a previous glTexImage2D	(or equivalent)	operation.

     GL_INVALID_OPERATION is generated if glCopyTexSubImage2DEXT is executed
     between the execution of glBegin and the corresponding execution of
     glEnd.







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glCopyTexSubImage2DEXT(3G)     OpenGL Reference	    glCopyTexSubImage2DEXT(3G)



ASSOCIATED GETS
     glGetTexImage


MACHINE	DEPENDENCIES
     RealityEngine, RealityEngine2, and	VTX systems support
     glCopyTexSubImage2DEXT with the following restrictions:

	  1.  Only level 0 is supported; other levels result in	a
	      GL_INVALID_VALUE error.

	  2.  The texel	offsets	and the	dimensions of the subimage must	be
	      multiples	of 32; otherwise a GL_INVALID_VALUE error is
	      generated.

	  3.  If glCopyTexSubImage2DEXT	is used	when a GLX video source	is the
	      read drawable (see glXMakeCurrentReadSGI), the X offset and Y
	      offset must both be 0 and	the subimage width must	be 768;
	      otherwise	a GL_INVALID_VALUE error is generated.

	  4.  GL_INTERLACE_SGIX	is not supported (see glEnable).

     On	InfiniteReality	systems, the width of the image	to be transferred to
     texture memory must be a multiple of 8.  This constraint will be lifted
     in	a future release, though transfers that	are a multiple of 8 in length
     will have somewhat	higher performance than	other transfers.

     Texture borders are not supported on InfiniteReality systems.  They will
     be	supported in a future release, however,	they will require large
     amounts of	texture	memory.	 Whenever possible, applications should	use
     borderless	textures and GL_CLAMP_TO_EDGE_SGIS wrap	mode.

     On	High Impact and	Maximum	Impact systems,	if the right side of the image
     to	be transferred to texture memory is not	the right side of the texture,
     then its index must be a multiple of 32, where index = xoffset+width.
     Otherwise it will generate	a GL_INVALID_VALUE error.

     The SGIX_interlace	extension is supported only on InfiniteReality systems
     and on RealityEngine, RealityEngine2, and VTX systems.

     Note that InfiniteReality systems currently do not	support	copying
     depth-format textures (used for shadow maps) from the framebuffer to
     texture memory.  This will	be fixed in a subsequent release.


SEE ALSO
     glTexImage2D, glTexSubImage2DEXT, glCopyPixels.








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