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GLTEXSUBIMAGE2D()					     GLTEXSUBIMAGE2D()

NAME
       glTexSubImage2D - specify a two-dimensional texture subimage

C SPECIFICATION
       void glTexSubImage2D( GLenum target,
			     GLint level,
			     GLint xoffset,
			     GLint yoffset,
			     GLsizei width,
			     GLsizei height,
			     GLenum format,
			     GLenum type,
			     const GLvoid *pixels )

       delim $$

PARAMETERS
       target	Specifies the target texture.  Must be GL_TEXTURE_2D.

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

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

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

       width	Specifies the width of the texture subimage.

       height	Specifies the height of	the texture subimage.

       format	Specifies  the	format	of the pixel data.  The	following sym-
		bolic values are accepted: GL_COLOR_INDEX,  GL_RED,  GL_GREEN,
		GL_BLUE, GL_ALPHA, GL_RGB, GL_RGBA, GL_LUMINANCE, and GL_LUMI-
		NANCE_ALPHA.

       type	Specifies the data type	of the pixel data.  The	following sym-
		bolic	values	 are   accepted:   GL_UNSIGNED_BYTE,  GL_BYTE,
		GL_BITMAP,   GL_UNSIGNED_SHORT,	  GL_SHORT,   GL_UNSIGNED_INT,
		GL_INT,	and GL_FLOAT.

       pixels	Specifies a pointer to the image data in memory.

DESCRIPTION
       Texturing maps a	portion	of a specified texture image onto each graphi-
       cal  primitive  for  which texturing is enabled.	 To enable and disable
       two-dimensional texturing, call glEnable	and  glDisable	with  argument
       GL_TEXTURE_2D.

       glTexSubImage2D redefines a contiguous subregion	of an existing two-di-
       mensional  texture  image.  The texels referenced by pixels replace the
       portion of the existing	texture	 array	with  x	 indices  xoffset  and
       $"xoffset"~+~"width"~-~1$, inclusive, and y indices yoffset and $"yoff-
       set"~+~"height"~-~1$,  inclusive.  This region may not include any tex-
       els outside the range of	the texture array as it	was originally	speci-
       fied.   It  is  not an error to specify a subtexture with zero width or
       height, but such	a specification	has no effect.

NOTES
       glTexSubImage2D is available only if the	GL version is 1.1 or greater.

       Texturing has no	effect in color	index mode.

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

ERRORS
       GL_INVALID_ENUM is generated if target is not GL_TEXTURE_2D.

       GL_INVALID_OPERATION is generated if the	texture	array has not been de-
       fined by	a previous glTexImage2D	operation.

       GL_INVALID_VALUE	is generated if	level is less than 0.

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

       GL_INVALID_VALUE	  is   generated  if  $"xoffset"  ~<~  ~-b$,  $("xoff-
       set"~+~"width") ~>~ (w~-~b)$, $"yoffset"	~<~ ~-b$, or  $("yoffset"  ~+~
       "height")  ~>~ (h~-~b)$.	 Where $w$ is the GL_TEXTURE_WIDTH, $h$	is the
       GL_TEXTURE_HEIGHT, and $b$ is the border	width of the texture image be-
       ing modified.  Note that	$w$ and	$h$ include twice the border width.

       GL_INVALID_VALUE	is generated if	width or height	is less	than 0.

       GL_INVALID_ENUM is generated if format is not an	accepted  format  con-
       stant.

       GL_INVALID_ENUM is generated if type is not a type constant.

       GL_INVALID_ENUM	is  generated  if  type	is GL_BITMAP and format	is not
       GL_COLOR_INDEX.

       GL_INVALID_OPERATION is generated if glTexSubImage2D  is	 executed  be-
       tween  the  execution  of  glBegin  and	the corresponding execution of
       glEnd.

ASSOCIATED GETS
       glGetTexImage
       glIsEnabled with	argument GL_TEXTURE_2D

SEE ALSO
       glCopyTexImage1D,  glCopyTexImage2D,  glCopyTexSubImage1D,   glCopyTex-
       SubImage2D,  glDrawPixels, glPixelStore,	glPixelTransfer, glTexEnv, gl-
       TexGen, glTexImage1D, glTexImage2D, glTexSubImage1D, glTexParameter

							     GLTEXSUBIMAGE2D()

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