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glCopyTexSubImage2D(3G)	       OpenGL Reference	       glCopyTexSubImage2D(3G)

NAME    [Toc]    [Back]

     glCopyTexSubImage2D - copy	a two-dimensional texture subimage

C SPECIFICATION    [Toc]    [Back]

     void glCopyTexSubImage2D( GLenum target,
			       GLint level,
			       GLint xoffset,
			       GLint yoffset,
			       GLint x,
			       GLint y,
			       GLsizei width,
			       GLsizei height )

PARAMETERS    [Toc]    [Back]

     target   Specifies	the target texture.  Must be GL_TEXTURE_2D.

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

     xoffset  Specifies	a texel	offset in the x	direction within the texture

     yoffset  Specifies	a texel	offset in the y	direction within the texture

     x,	y     Specify the window coordinates of	the lower left corner of the
	      rectangular region of pixels to be copied.

     width    Specifies	the width of the texture subimage.

     height   Specifies	the height of the texture subimage.

DESCRIPTION    [Toc]    [Back]

     glCopyTexSubImage2D 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 glTexSubImage2D).

     The screen-aligned	pixel rectangle	with lower left	corner at (x, y) and
     with 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.

     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

									Page 1

glCopyTexSubImage2D(3G)	       OpenGL Reference	       glCopyTexSubImage2D(3G)

     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

     No	change is made to the internalformat, width, height, or	border
     parameters	of the specified texture array or to texel values outside the
     specified subregion.

NOTES    [Toc]    [Back]

     glCopyTexSubImage2D is available only if the GL version is	1.1 or

     Texturing has no effect in	color index mode.

     glPixelStore and glPixelTransfer modes affect texture images in exactly
     the way they affect glDrawPixels.

     When the GL_ARB_imaging extension is supported, the RGBA components read
     from the framebuffer may be processed by the imaging pipeline.  See
     glTexImage1D for specific details.

ERRORS    [Toc]    [Back]

     GL_INVALID_ENUM is	generated if target is not GL_TEXTURE_2D.

     GL_INVALID_OPERATION is generated if the texture array has	not been
     defined by	a previous glTexImage2D	or glCopyTexImage2D operation.

     GL_INVALID_VALUE is generated if level is less than 0.

     GL_INVALID_VALUE may be generated if level	is greater than	log max, where
     max is the	returned value of GL_MAX_TEXTURE_SIZE.

     GL_INVALID_VALUE is generated if x	<  -b or if y <	 -b, where b is	the
     border width of the texture array.

     GL_INVALID_VALUE is generated if xoffset <	-b,
     (xoffset +	width) > (w - b), yoffset <  -b, or
     (yoffset +	height)	> (h - b), where w is the GL_TEXTURE_WIDTH, h is the
     GL_TEXTURE_HEIGHT,	and b is the GL_TEXTURE_BORDER of the texture image
     being modified.  Note that	w and h	include	twice the border width.

     GL_INVALID_OPERATION is generated if glCopyTexSubImage2D is executed
     between the execution of glBegin and the corresponding execution of

									Page 2

glCopyTexSubImage2D(3G)	       OpenGL Reference	       glCopyTexSubImage2D(3G)

ASSOCIATED GETS    [Toc]    [Back]

     glIsEnabled with argument GL_TEXTURE_2D

     RealityEngine, RealityEngine2, and	VTX systems do not support color
     matrix transformations on images as they are loaded to or read back from
     texture memory.

     RealityEngine, RealityEngine2, and	VTX systems support
     glCopyTexSubImage2D and glCopyTexSubImage2DEXT with the following

	  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

	  3.  If glCopyTexSubImage2D or	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, there is a performance	benefit	when the width
     of	the image to be	transferred to texture memory is a multiple of 8.

     Texture borders are not supported on InfiniteReality systems.
     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, on RealityEngine,	RealityEngine2,	and VTX	systems, on Octane2
     VPro systems, and on O2 systems.

     The INGR_interlace_read extension is supported only on Octane2 VPro
     systems, and on O2	systems.

     On	O2 systems, when the current read drawable is a	DM pbuffer, using
     glCopyTexSubImage2D or glCopyTexSubImage2DEXT to copy into	a full texture
     image whose dimensions and	format match those of the pbuffer causes a
     copy-by-reference.	 This has performance advantages, especially for

									Page 3

glCopyTexSubImage2D(3G)	       OpenGL Reference	       glCopyTexSubImage2D(3G)

     video-generated DMbuffers,	because	it provides a DMA path for updating
     textures.	Following the copy, rendering to the pbuffer or	otherwise
     modifying the DMbuffer, will directly affect texture memory.  However,
     this behavior is essentially an unspecified side-effect of	the
     implementation on O2, and cannot be used on other systems.

SEE ALSO    [Toc]    [Back]

     glCopyPixels, glCopyTexImage1D, glCopyTexImage2D, glCopyTexSubImage1D,
     glCopyTexSubImage3D, glPixelStore,	glPixelTransfer, glReadBuffer,
     glTexEnv, glTexGen, glTexImage1D, glTexImage2D, glTexImage3D,
     glTexParameter, glTexSubImage1D, glTexSubImage2D, glTexSubImage3D

									PPPPaaaaggggeeee 4444
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