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glCopyTexImage2D(3G)	       OpenGL Reference		  glCopyTexImage2D(3G)


NAME    [Toc]    [Back]

     glCopyTexImage2D -	copy pixels into a 2D texture image

C SPECIFICATION    [Toc]    [Back]

     void glCopyTexImage2D( GLenum target,
			    GLint level,
			    GLenum internalformat,
			    GLint x,
			    GLint y,
			    GLsizei width,
			    GLsizei height,
			    GLint border )

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.

     internalformat  Specifies the internal format of the texture.  Must be
		     one of the	following symbolic constants:  GL_ALPHA,
		     GL_ALPHA4,	GL_ALPHA8, GL_ALPHA12, GL_ALPHA16,
		     GL_LUMINANCE, GL_LUMINANCE4, GL_LUMINANCE8,
		     GL_LUMINANCE12, GL_LUMINANCE16, GL_LUMINANCE_ALPHA,
		     GL_LUMINANCE4_ALPHA4, GL_LUMINANCE6_ALPHA2,
		     GL_LUMINANCE8_ALPHA8, GL_LUMINANCE12_ALPHA4,
		     GL_LUMINANCE12_ALPHA12, GL_LUMINANCE16_ALPHA16,
		     GL_INTENSITY, GL_INTENSITY4, GL_INTENSITY8,
		     GL_INTENSITY12, GL_INTENSITY16, GL_RGB, GL_R3_G3_B2,
		     GL_RGB4, GL_RGB5, GL_RGB8,	GL_RGB10, GL_RGB12, GL_RGB16,
		     GL_RGBA, GL_RGBA2,	GL_RGBA4, GL_RGB5_A1, GL_RGBA8,
		     GL_RGB10_A2, GL_RGBA12, or	GL_RGBA16.

     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	image.	Must be	0 or
		      n
		     2	+ 2*border for some integer n.

     height	     Specifies the height of the texture image.	 Must be 0 or
		      m
		     2	+ 2*border for some integer m.

     border	     Specifies the width of the	border.	 Must be either	0 or
		     1.

DESCRIPTION    [Toc]    [Back]

     glCopyTexImage2D defines a	two-dimensional	texture	image with pixels from
     the current GL_READ_BUFFER.




									Page 1






glCopyTexImage2D(3G)	       OpenGL Reference		  glCopyTexImage2D(3G)



     The screen-aligned	pixel rectangle	with lower left	corner at (x, y) and
     with a width of width + 2 * border	and a height of	height + 2 * border
     defines the texture array at the mipmap level specified by	level.
     internalformat specifies the internal format of the texture array.

     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
     array.

     Pixel ordering is such that lower x and y screen coordinates correspond
     to	lower s	and t texture coordinates.

     If	any of the pixels within the specified rectangle of the	current
     GL_READ_BUFFER are	outside	the window associated with the current
     rendering context,	then the values	obtained for those pixels are
     undefined.

NOTES    [Toc]    [Back]

     glCopyTexImage2D is available only	if the GL version is 1.1 or greater.

     Texturing has no effect in	color index mode.

     1,	2, 3, and 4 are	not accepted values for	internalformat.

     An	image with height or width of 0	indicates a NULL texture.

     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_VALUE is generated if level is less than 0.

     GL_INVALID_VALUE may be generated if level	is greater than	log max, where
								   2
     max is the	returned value of GL_MAX_TEXTURE_SIZE.

     GL_INVALID_VALUE is generated if width or height is less than 0, greater
     than 2 + GL_MAX_TEXTURE_SIZE, or if width or height cannot	be represented
	 k
     as	2  + 2 * border	for some integer k.

     GL_INVALID_VALUE is generated if border is	not 0 or 1.

     GL_INVALID_VALUE is generated if internalformat is	not one	of the
     allowable values.

     GL_INVALID_OPERATION is generated if glCopyTexImage2D is executed between
     the execution of glBegin and the corresponding execution of glEnd.




									Page 2






glCopyTexImage2D(3G)	       OpenGL Reference		  glCopyTexImage2D(3G)


ASSOCIATED GETS    [Toc]    [Back]

     glGetTexImage
     glIsEnabled with argument GL_TEXTURE_2D


MACHINE	DEPENDENCIES
     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 glCopyTexImage2D
     and glCopyTexImage2DEXT with the following	restrictions:

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

	  2.  glCopyTexImage2D and glCopyTexImage2DEXT cannot be used if a GLX
	      video source is the current read drawable	(see
	      glXMakeCurrentReadSGI).  Executing it will generate a
	      GL_INVALID_OPERATION error.

	  3.  GL_INTERLACE_SGIX	is not supported (see glEnable).

	  4.  Borders are not supported; hence the width of the	border should
	      be 0.

     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.

     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	High Impact and	Maximum	Impact systems the number of bits per
     component,	represented internally,	is the same for	all components and
     will be 4,	8, or 12 bits per component. All specified internal formats
     will receive an equal or greater representation in	this scheme, up	to the
     12-bit limit.  High Impact	and Maximum Impact on Indigo2 systems do not
     support texture internal formats of the type GL_INTENSITY or GL_ALPHA,
     although High Impact and Maximum Impact on	Octane systems do support
     these types.

     High Impact and Maximum Impact on Indigo2 systems without the TRAM	option
     card support 4 bits per component for GL_RGB and GL_RGBA, 4/8 bits	per
     component for GL_LUMINANCE_ALPHA, and 4/8/12 bits per component for



									Page 3






glCopyTexImage2D(3G)	       OpenGL Reference		  glCopyTexImage2D(3G)



     GL_LUMINANCE.

SEE ALSO    [Toc]    [Back]

      
      
     glCopyPixels, glCopyTexImage1D, glCopyTexSubImage1D, glCopyTexSubImage2D,
     glPixelStore, glPixelTransfer, glTexEnv, glTexGen,	glTexImage1D,
     glTexImage2D, glTexSubImage1D, glTexSubImage2D, glTexParameter


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